7820A Advanced User Guide
Agilent 7820A
Gas Chromatograph
Advanced User Guide
Agilent Technologies
Notices
© Agilent Technologies, Inc. 2009-2011
Technology Licenses
No part of this manual may be reproduced
in any form or by any means (including
electronic storage and retrieval or translation into a foreign language) without prior
agreement and written consent from
Agilent Technologies, Inc. as governed by
United States and international copyright
laws.
The hardware and/or software described in
this document are furnished under a
license and may be used or copied only in
accordance with the terms of such license.
Manual Part Number
G4350-90020
Edition
Third edition, June 2011
Second edition, January 2010
First edition, March 2009
Printed in China
Agilent Technologies, Inc.
412 Ying Lun Road
Waigoaqiao Freed Trade Zone
Shanghai 200131 P.R.China
Restricted Rights
If software is for use in the performance of
a U.S. Government prime contract or subcontract, Software is delivered and
licensed as “Commercial computer software” as defined in DFAR 252.227-7014
(June 1995), or as a “commercial item” as
defined in FAR 2.101(a) or as “Restricted
computer software” as defined in FAR
52.227-19 (June 1987) or any equivalent
agency regulation or contract clause. Use,
duplication or disclosure of Software is
subject to Agilent Technologies’ standard
commercial license terms, and non-DOD
Departments and Agencies of the U.S. Government will receive no greater than
Restricted Rights as defined in FAR
52.227-19(c)(1-2) (June 1987). U.S. Government users will receive no greater than
Limited Rights as defined in FAR 52.227-14
(June 1987) or DFAR 252.227-7015 (b)(2)
(November 1995), as applicable in any
technical data.
Safety Notices
CAUTION
A CAUTION notice denotes a hazard. It
calls attention to an operating
procedure, practice, or the like that, if
not correctly performed or adhered to,
could result in damage to the product
or loss of important data. Do not
proceed beyond a CAUTION notice
until the indicated conditions are fully
understood and met.
WA R N I N G
A WARNING notice denotes a hazard.
It calls attention to an operating
procedure, practice, or the like that, if
not correctly performed or adhered to,
could result in personal injury or
death. Do not proceed beyond a
WARNING notice until the indicated
conditions are fully understood and
met.
Firmware Version
This manual is written for 7820A GCs using
firmware version A.01.12.
Contents
1
Software Keypad
Using the Software Keypad
2
12
Programming
Run Time Programming 14
Using run time events 14
Programming run time events
The run table 15
Adding events to the run table
Editing events in the run table
Deleting run time events 16
15
15
15
Clock Time Programming 17
Using clock time events 17
Programming clock time events
Adding events to the clock table
Editing clock time events 18
Deleting clock time events 18
Post Run Programming 19
To enable a post run program
To disable a post run program
3
17
18
19
19
Configuration
About Configuration 22
Assigning GC resources to a device 22
Setting configuration properties 23
General Topics 24
Unlock the GC Configuration
Ignore Ready = 24
Information displays 25
Unconfigured: 25
Oven 26
To configure the oven
24
26
Front Inlet/Back Inlet 27
To configure the Gas type
27
Column # 28
To configure a single column 28
To view a summary of column connections
Advanced User Guide
30
3
Front Detector/Back Detector 31
To configure the makeup/reference gas
Lit offset 31
To configure the FPD heaters 31
To ignore the FID or FPD ignitor 32
Analog Out 33
Fast peaks
31
33
Valve Box 34
To assign a GC power source to a valve box heater
34
Thermal Aux 35
To assign a GC power source to an Aux thermal zone
To configure a MSD transfer line heater 35
To configure a nickel catalyst heater 35
PCM A/PCM B 37
To assign a GC communication source to a PCM
To configure a PCM 37
35
37
Status 38
The Ready/Not Ready status table 38
The setpoint status table 38
To configure the setpoint status table 38
Time 39
To set time and date 39
To use the stopwatch 39
Valve # 40
To configure a valve
40
Front injector/Back injector
Instrument
4
41
42
Options
About Options
44
Calibration 45
Maintaining EPC calibration—inlets, detectors, and PCM
To zero all pressure sensors in all modules 47
Column calibration 47
Communication 51
Configuring the IP address for the GC
Keyboard and Display
4
45
51
52
Advanced User Guide
5
Chromatographic Checkout
About Chromatographic Checkout
54
To Prepare for Chromatographic Checkout
To Check FID Performance
56
To Check TCD Performance
60
To Check NPD Performance
64
To Check uECD Performance
55
68
To Check FPD Performance (Sample 5188-5953)
6
72
Methods and Sequences
Creating Methods 80
To program a method 80
To program the ALS 81
To save a method 81
To load a stored method 81
Method mismatch 81
Creating Sequences 83
About the priority sequence 83
To program a sequence 83
To program a priority sequence 84
To program an ALS subsequence 85
To program a valve subsequence 85
To program post sequence events 85
To save a sequence 86
To load a stored sequence 86
To determine sequence status 86
To start a sequence 86
To pause and resume a sequence 87
To stop a sequence 87
To abort a sequence 87
7
Checking for Leaks
Preparing the GC for Maintenance 90
Column and oven preparation 90
Inlet preparation 90
Detector preparation 90
Leak Check Tips
91
To Check for External Leaks
To Check for GC Leaks
Advanced User Guide
92
93
5
To Perform a SS Inlet Pressure Decay Test
94
To Correct Leaks in the Split Splitless Inlet
98
To Perform a PP Inlet Pressure Decay Test
99
To Correct Leaks in the Packed Column Inlet
8
103
Inlets
Using Hydrogen
Inlet Overview
106
107
Carrier Gas Flow Rates
108
About Gas Saver 109
To use gas saver 109
Pre Run and Prep Run 110
The [Prep Run] key 110
Auto Prep Run 111
About Heaters
112
About the Split/Splitless Inlet 114
Septum tightening (S/SL) 114
Split/Splitless inlet split mode overview 114
Split/Splitless inlet splitless mode overview 115
The S/SL inlet pulsed split and splitless modes 116
Split/Splitless inlet split mode minimum operating pressures
Selecting the correct S/SL inlet liner 118
Vapor Volume Calculator 120
Setting parameters for the S/SL split mode 120
Selecting parameters for the S/SL splitless mode 121
Setting parameters for the S/SL splitless mode 122
Setting parameters for the S/SL pulsed modes 123
About the Packed Column Inlet
Setting parameters 124
9
117
124
Columns and Oven
About the Oven
Oven safety
128
128
Configuring the Oven
129
About Oven Temperature Programming 130
Programming setpoints 130
Oven ramp rates 131
Setting the oven parameters for constant temperature 131
Setting the oven parameters for ramped temperature 132
6
Advanced User Guide
About Columns 133
Selecting the correct packed glass column type 133
About the column modes 133
Select a column mode 134
Setting the column parameters for constant flow or constant
pressure 135
Enter a flow or pressure program (optional) 135
Programming column pressure or flow 136
Nickel Catalyst Tube 137
About the nickel catalyst tube 137
Nickel catalyst gas flows 137
Setting temperatures for the nickel catalyst tube
10
138
Detectors
About Makeup Gas
140
About the FID 141
How FID units are displayed in Agilent data systems and on the GC
To light the FID flame 143
To extinguish the FID flame 143
FID automatic reignition (Lit offset) 143
Recommended starting conditions for new FID methods 143
Setting parameters for FID 144
142
About the TCD 146
TCD pneumatics 148
TCD carrier, reference, and makeup gas 148
TCD gas pressures 149
Selecting reference and makeup flows for the TCD 150
Chemically active compounds reduce TCD filament life 150
Changing the TCD polarity during a run 151
Detecting hydrogen with the TCD using helium carrier gas 151
Setting parameters for the TCD 152
About the uECD 154
uECD safety and regulatory information 154
uECD warnings 155
Safety precautions when handling uECDs 156
uECD gas flows 157
uECD linearity 157
uECD detector gas 157
uECD temperature 158
uECD analog output 158
Recommended starting conditions for new uECD methods
uECD makeup gas notes 159
Advanced User Guide
158
7
uECD temperature programming
Setting parameters for the uECD
159
159
About the NPD 160
NPD flows and general information 160
NPD flow, temperature, and bead recommendations
NPD required gas purity 162
Setting parameters for the NPD 163
Selecting an NPD bead type 164
Selecting an NPD jet 165
To configure the NPD 166
Automatically adjusting NPD bead voltage 167
Setting NPD adjust offset on the clock table 168
Aborting NPD adjust offset 168
Extending the NPD bead life 168
Setting the initial bead voltage for new beads 169
Setting NPD bead voltage manually (optional) 169
About the FPD 171
FPD linearity 172
FPD Lit Offset 172
Starting Up and Shutting Down the FPD
FPD photomultiplier protection 172
FPD optical filters
172
Inlet liners for use with the FPD 173
FPD temperature considerations 173
FPD gas purity 173
FPD gas flows 173
Lighting the FPD flame 174
Setting parameters for the FPD 175
11
172
Valves
The Valve Box 178
Heating the valves 178
Valve temperature programming
Valve Control 179
The valve drivers 179
The internal valve drivers
Valve Types
178
179
181
Configuring a Valve
182
Controlling a Valve 183
From the keyboard 183
From the run or clock time tables
8
161
183
Advanced User Guide
Gas sampling valve
12
183
Cables
About Cables and Back Panel Connectors
Back panel connectors 186
Sampler connectors 186
Signal connector 186
REMOTE connector 187
TEST PORT connector 187
LAN connector 187
186
Using the Remote Start/Stop cable 188
Connecting Agilent products 188
Connecting non-Agilent products 188
Connecting Cables
191
Cable Diagrams 193
Analog cable, general use 193
Remote start/stop cable 193
13
GC Output Signals
About Signals
196
Analog Signals 197
Analog zero 197
Analog range 197
Analog data rates 198
Selecting fast peaks (analog output)
Digital Signals 200
Digital zero 200
Signal Freeze and Resume 200
Data rates with Agilent data systems
Zero Init Data Files 203
14
199
201
Miscellaneous Topics
About Pressure Control 206
Pressure units 206
To Use the Stopwatch
207
Service Mode 208
Service Reminders 208
Other functions 208
Advanced User Guide
9
10
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
1
Software Keypad
Agilent Technologies
11
1
Software Keypad
Using the Software Keypad
The Agilent software keypad (remote controller) software
provides the ability to program and use the 7820A Gas
Chromatograph (GC). Refer to the Operating Guide for
instructions for its installation and use.
Figure 1
Software keypad (remote controller)
All instructions in this manual assume the use of the
software keypad unless otherwise noted.
12
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
2
Programming
Run Time Programming 14
Using run time events 14
Programming run time events 15
The run table 15
Adding events to the run table 15
Editing events in the run table 15
Deleting run time events 16
Clock Time Programming 17
Using clock time events 17
Programming clock time events 17
Adding events to the clock table 18
Editing clock time events 18
Deleting clock time events 18
Post Run Programming 19
Agilent Technologies
13
2
Programming
Run Time Programming
Run time programming allows certain setpoints to change
automatically during a run as a function of the
chromatographic run time. Thus an event that is
programmed to occur at 2 minutes will occur 2 minutes
after every injection.
Its uses include:
• Controlling column switching or other valves
• Changing analog signal definition, zero, or range
• Controlling an auxiliary pressure channel
• Changing polarity of a thermal conductivity detector
(TCD)
• Turning the hydrogen flow to a nitrogen- phosphorus
detector (NPD) on or off
• Switching digital signal output (requires an Agilent data
system)
• Pausing (“freezing”) and resuming digital signal output
(requires an Agilent data system)
The changes are entered into a run table that specifies the
setpoint to be changed, the time for the change, and the new
value. At the end of the chromatographic run, most setpoints
changed by a run time table are returned to their original
values.
Valves can be run time programmed but are not restored to
their starting position at the end of the run. You must
program the reset operation in the run table if this action is
desired. See “From the run or clock time tables” on
page 183.
Using run time events
The [Run Table] key is used to program the following timed
events.
• Valves (1- 2)
• Analog signal definition, zero, and range
• TCD negative polarity (on/off)
• Detector gas flow (on/off), including NPD H2 fuel gas
14
Advanced User Guide
2
Programming
Programming run time events
1 Press [Run Table].
2
Press [Mode/Type] to see the available run time events.
3
Scroll to the event to be programmed. Press [Enter].
4
Enter values for the Time: and the other parameter. Press
[Enter] after each entry.
5
Press [Mode/Type] to add another event. Press [Status] to
terminate entries.
The run table
The programmed events are arranged in order of execution
time in the Run Table. This is a brief example:
RUN TABLE (1 of 3)
Time:
0.10
Valve #2
On
RUN TABLE (2 of 3)
Time:
3
Analog signal 2 range 2
RUN TABLE (3 of 3)
Time:
4.20
Valve #2
Off
Event 1 rotates a valve.
Event 2 adjusts the signal
range.
Event 3 resets Valve #2 to its
original position in preparation
for another run. Valves do not
reset automatically.
Adding events to the run table
1 To add new events to the run table, press [Mode/Type]
while on the Time: line of any entry.
2
Select the event type.
3
Set appropriate Time: and other parameters. Some require
numbers; others require [On/Yes] or [Off/No].
4
Repeat until all entries are added. Events are
automatically placed in order by execution time.
Editing events in the run table
1 Press [Run Table].
Advanced User Guide
2
Move the cursor to the event you want to change.
3
To edit the time for an event, move the cursor to the line
labeled Time:. Type the desired time and press [Enter].
15
2
Programming
4
To edit a setpoint value, scroll to the setpoint line. Press
[On/Yes] or [Off/No] or enter a numeric value for the
setpoint. Press [Enter].
Deleting run time events
1 Press [Run Table].
16
2
From within this table press [Delete] to delete events
from the run time table. You will be asked to confirm the
deletion.
3
Press [On/Yes] to delete the current timed event; press
[Off/No] to cancel this operation.
4
To delete the entire table, press [Delete][Run Table].
Advanced User Guide
2
Programming
Clock Time Programming
Clock time programming allows certain setpoints to change
automatically at a specified time during a 24- hour day. Thus,
an event programmed to occur at 14:35 hours will occur at
2:35 in the afternoon. A running analysis or sequence has
precedence over any clock table events occurring during this
time. Such events are not executed.
Possible clock time events include:
• Valve control
• Method and sequence loading
• Starting sequences
• Initiating blank and prep runs
• Column compensation changes
• Adjustments of the detector offset
Using clock time events
The Clock Table function allows you to program events to
occur during a day based on the 24- hour clock. Clock table
events that would occur during a run or sequence are
ignored.
For example, the clock table could be used to make a blank
run before you even get to work in the morning.
Programming clock time events
1 Press [Clock Table].
2
Press [Mode/Type] to see the available clock time events.
3
Scroll to the parameter to be programmed.
4
Edit Time: and the setpoints for this event.
5
Press [Mode/Type] to add another event. Press [Status] to
terminate entries.
When the clock event is executed, a confirming message
appears.
Advanced User Guide
17
2
Programming
Adding events to the clock table
1 Press [Clock Table].
2
Press [Mode/Type]. When entries are added, they are
automatically ordered chronologically.
3
Select the event type.
4
Set appropriate parameters.
5
Repeat this process until all entries are added.
Editing clock time events
1 Press [Clock Table] to view all events programmed.
2
Scroll to the event you want to change.
3
To edit the time for an event, move the cursor to the line
labelled Time: and type the desired time.
4
To edit a setpoint value, scroll to the setpoint item. Press
[On/Yes] or [Off/No], or enter a numerical value for the
setpoint.
Deleting clock time events
1 Press [Clock Table].
2
Use [Delete] to remove events from the clock time table.
You will be asked to confirm the deletion.
3
Press [On/Yes] to delete the current timed event; press
[Off/No] to cancel this operation.
To delete the entire table, press [Delete][Clock Table].
18
Advanced User Guide
Programming
2
Post Run Programming
This function can be used with both isothermal and
programmed methods. Post run is a period that begins at the
end of the normal run. The parameters include:
• Time—How long is the post run period?
• Oven Temperature—What is the oven temperature during the
post run period?
• Column n pres—For a column controlled in a pressure mode,
enter the pressure for this column during the post run
period.
• Column n flow—For a column controlled in a flow mode,
enter the flow rate for this column during the post run
period.
Post run may be used to clean out a column in preparation
for the next run, backflush a column to eliminate
high- boilers, and other functions.
When the Post run Time elapses, the GC returns to the initial
state defined in the current method.
To enable a post run program
1 Press [Post Run].
2
Type a non- zero time for the post run duration and press
[Enter]. The post run parameters available for the current
GC configuration appear.
3
Scroll to each desired parameter, type the value for the
post run period, and press [Enter].
To disable a post run program
1 Press [Post Run].
2
Advanced User Guide
Type a 0 as the post run time and press [Enter].
19
2
20
Programming
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
3
Configuration
About Configuration 22
Assigning GC resources to a device 22
Setting configuration properties 23
General Topics 24
Unlock the GC Configuration 24
Ignore Ready = 24
Information displays 25
Unconfigured: 25
Oven 26
Front Inlet/Back Inlet 27
Column # 28
To configure a single column 28
Front Detector/Back Detector 31
Lit offset 31
To configure the FPD heaters 31
Analog Out 33
Fast peaks 33
Valve Box 34
Thermal Aux 35
To configure a MSD transfer line heater 35
To configure a nickel catalyst heater 35
PCM A/PCM B 37
Status 38
The Ready/Not Ready status table 38
The setpoint status table 38
Time 39
Valve # 40
Front injector/Back injector 41
Instrument 42
Agilent Technologies
21
3
Configuration
About Configuration
Configuration is a two- part process for most GC accessory
devices that require power and/or communication resources
from the GC. In the first part of the configuration process, a
power and/or communication resource is assigned to the
device. The second part of the configuration process allows
setting of any configuration properties associated with the
device.
Assigning GC resources to a device
A hardware device requiring but not assigned GC resources
is given a mode of Unconfigured by the GC. Once you assign
GC resources to a device, the GC gives the device a mode of
Configured, allowing you to access other property settings (if
any) for the device.
To assign GC resources to a device with an Unconfigured
mode:
1 Unlock the GC configuration. Press [Options], select
Keyboard & Display and press [Enter]. Scroll down to Hard
Configuration Lock and press [Off/No].
2
Press [Config] on the GC keypad and select a device from
the list, then press [Enter].
The [Config] key opens a menu similar to this:
Oven
Front inlet
Back Inlet
Column #
Front detector
Back detector
Analog out
Valve Box
Thermal Aux 1
PCM A
PCM B
Status
Time
Valve #
Injector
Instrument
In many cases you can move directly to the item of
interest by pressing [Config][device].
22
Advanced User Guide
Configuration
3
3
When the Configure Device Display opens, the cursor
should be on the Unconfigured field. Press [Mode/Type] and
follow the GC prompts to assign resources to the device.
4
After assigning resources, the GC prompts for you to
power cycle the GC. Turn the GC power switch off and
then on.
When the GC starts, select the device just assigned the GC
resources for further configuration if needed. When accessed,
its mode should indicate Configured and the other
configuration properties are displayed.
Setting configuration properties
A device’s configuration properties are constant for an
instrument hardware setup unlike method settings which can
change from sample run to sample run. An example of a
configuration setting is the gas type flowing through a
pneumatic device or the operation temperate limit of a
device.
To change the setting configuration properties for a
Configured device:
1 Press [Config] on the GC keypad and select a device from
the list, then press [Enter].
In many cases you can move directly to the item of
interest by pressing [Config][device].
2
Advanced User Guide
Scroll to the device setting and change the property. This
can involve making a selection from a list using
[Mode/Type], using [On/Yes] or [Off/No], or entering a
numeric value. Press [Info] for help on changing numeric
settings, or see the section of this document describing
the specific configuration of the device.
23
3
Configuration
General Topics
Unlock the GC Configuration
Accessory devices including inlets, detectors, pressure
controllers (PCM), and temperature control loops (Thermal
AUX) have electrical connections to a power source and/or
the communication bus in the GC. These devices must be
assigned GC resources before they can be used. Before
assigning resources to a device, you must first unlock the GC
configuration. If you try to configure an Unconfigured device
without unlocking the GC configuration, the GC displays the
message CONFIGURATION IS LOCKED Go to Keyboard options to
unlock.
It is also necessary to unlock the GC configuration if you are
removing the GC resources from a Configured device. This
action returns the device state to Unconfigured.
To unlock the GC configuration, press [Options], select
Keyboard & Display and press [Enter]. Scroll down to Hard
Configuration Lock and press [Off/No].
The GC configuration remains unlocked until the GC is
power cycled off and on.
Ignore Ready =
The states of the various hardware elements are among the
factors that determine whether the GC is Ready for analysis.
Under some circumstances, you may not wish to have a
specific element readiness considered in the GC readiness
determination. This parameter lets you make that choice.
The following elements allow readiness to be ignored: inlets,
detectors, the oven, PCM, and auxiliary EPC modules.
For example, suppose an inlet heater is defective but you
don’t plan to use that inlet today. By setting Ignore Ready =
TRUE for that inlet, you can use the rest of the GC. After the
heater is repaired, set Ignore Ready = FALSE or the run could
start before that inlet’s conditions are ready.
To ignore an element's readiness, press [Config], then select
the element. Scroll to Ignore Ready and press [On/Yes] to set it
to True.
To consider an element's readiness, press [Config], then select
the element. Scroll to Ignore Ready and press [Off/No] to set it
to False.
24
Advanced User Guide
3
Configuration
Information displays
Below are some examples of configuration displays:
[ EPC1 ] = (INLET) (SS) EPC #1 is used for an inlet of type
split/splitless. It is not available for other uses.
[ EPC3 ] = (DET-EPC) (FID)
gases to an FID.
EPC #3 is controlling detector
FINLET (OK) 68 watts 21.7 This heater is connected to the
front inlet. Status = OK, meaning that it is ready for use. At
the time that the GC was turned on, the heater was drawing
68 watts and the inlet temperature was 21.7 °C.
[ F-DET ] = (SIGNAL) (FID)
detector is type FID.
The signal board for the front
Unconfigured:
Accessory devices requiring GC power or communication
must be assigned these GC resources before they can be
used. To make this hardware element usable, first “Unlock
the GC Configuration” on page 24 then go to the Unconfigured
parameter and press [Mode/Type] to install it. If the
hardware element you are configuring requires selection of
additional parameters, the GC asks for that selection. If no
parameters are required, press [Enter] at the GC prompt to
install that element. You are required to power the GC off
and then power the GC on to complete this configuration.
After restarting the GC, a message reminding you of this
change and its effect on the default method is displayed. If
needed, change your methods to accommodate the new
hardware.
Advanced User Guide
25
3
Configuration
Oven
See “Unconfigured:” on page 25 and “Ignore Ready =” on
page 24.
Maximum temperature Sets an upper limit to the oven
temperature. Used to prevent accidental damage to columns.
The range is 70 to 425 °C.
Equilibration time The time after the oven approaches its
setpoint before the oven is declared Ready. The range is 0 to
999.99 minutes. Used to ensure that the oven contents have
stabilized before starting another run.
To configure the oven
1 Press [Config][Oven].
26
2
Scroll to Maximum temperature. Enter a value and press
[Enter].
3
Scroll to Equilibration time. Enter a value and press [Enter].
Advanced User Guide
Configuration
3
Front Inlet/Back Inlet
See “Unconfigured:” on page 25 and “Ignore Ready =” on
page 24.
To configure the Gas type
The GC needs to know what carrier gas is being used.
1 Press [Config][Front Inlet] or [Config][Back Inlet].
2
Scroll to Gas type and press [Mode/Type].
3
Scroll to the gas you will use. Press [Enter].
This completes carrier gas configuration.
Advanced User Guide
27
3
Configuration
Column #
Length The length, in meters, of a capillary column. Enter 0
for a packed column or if the length is not known.
Diameter The inside diameter, in millimeters, of a capillary
column. Enter 0 for a packed column.
Film thickness The thickness, in millimeters, of the
stationary phase for capillary columns.
Inlet
Identifies the source of gas for the column.
Outlet Identifies the device into which the column effluent
flows.
Thermal zone Identifies the device that controls the
temperature of the column.
To configure a single column
You define a capillary column by entering its length,
diameter, and film thickness. You then enter the device
controlling the pressure at the Inlet (end of the column), the
device controlling the pressure at the column Outlet, and the
Thermal zone that controls its temperature.
With this information, the instrument can calculate the flow
through the column. This has great advantages when using
capillary columns because it becomes possible to:
• Enter split ratios directly and have the instrument
calculate and set the appropriate flow rates.
• Enter flow rate or head pressure or average linear
velocity. The instrument calculates the pressure needed to
achieve the flow rate or velocity, sets that, and reports all
three values. (Split/splitless inlet only.)
• Perform splitless injections with no need to measure gas
flows.
• Choose any column mode. If the column is not defined,
your choices are limited.
28
Advanced User Guide
3
Configuration
Except for the simplest configurations, such as a column
connected to a specific inlet and detector, we recommend
that you begin by making a sketch of how the column will be
connected.
1 Press [Config][Col #] then enter the number of the column
to be configured.
2
Scroll to the Length line, type the column length, in
meters, followed by [Enter].
3
Scroll to Diameter, type the column inside diameter in
microns, followed by [Enter].
4
Scroll to Film thickness, type the film thickness in microns,
followed by [Enter]. The column is now defined.
If you do not know the column dimensions—they are
usually supplied with the column—or if you do not wish
to use the GC calculating features, enter 0 for either
Length or Diameter. The column will be not defined.
5
Scroll to Inlet. Press [Mode/Type] to select a gas pressure
control device for this end of the column. Selections
include the installed GC inlets and installed PCM
channels.
Select the appropriate gas pressure control device and
press [Enter].
6
Scroll to Outlet. Press [Mode/Type] to select a gas pressure
control device for this end of the column. When a
detector is selected, the outlet end of the column is
controlled at 0 psig for the FID, TCD, FPD, NPD, and
uECD or vacuum for the MSD.
Select the appropriate gas pressure control device and
press [Enter].
7
Scroll to Thermal zone. Press [Mode/Type] to see the
available choices. In most cases this will be GC oven, but
you may have an MSD transfer line heated by an
auxiliary zone, valves in a separately- heated valve box or
other configurations.
Select the appropriate Thermal zone and press [Enter].
This completes configuration for a single capillary column.
Additional notes on column configuration
Packed columns should be configured as column not defined.
To do this, enter 0 for either column length or column
diameter.
Advanced User Guide
29
3
Configuration
You should check configurations for all columns to verify
that they specify the correct pressure control device at each
end. The GC uses this information to determine the flow
path of the carrier gas. Only configure columns that are in
current use in your GC’s carrier gas flow path. Unused
columns configured with the same pressure control device as
a column in the current flow path cause incorrect flow
results.
It is possible, and sometimes appropriate, to configure both
installed columns to the same inlet.
Some pneumatic setpoints change with oven temperature
because of changes in column resistance and in gas viscosity.
This may confuse users who observe pneumatics setpoints
changing when their oven temperature changes. However, the
flow condition in the column remains as specified by the
column mode (constant flow or pressure, ramped flow or
pressure) and the initial setpoint values.
To view a summary of column connections
To view a summary of column connections, press [Config][Col
#], then press [Enter]. The GC lists the column connections,
for example:
Front Inlet -> Column 1
Column 1 -> Front detector
30
Advanced User Guide
3
Configuration
Front Detector/Back Detector
See Ignore Ready = and “Unconfigured:” on page 25.
To configure the makeup/reference gas
The makeup gas line of your detector parameter list changes
depending on your instrument configuration.
If you have an inlet with the column not defined, the
makeup flow is constant. If you are operating with column
defined, you have a choice of two makeup gas modes. See
“About Makeup Gas” on page 140 for details.
1 Press [Config][device], where [device] is one of the
following:
• [Front Det]
• [Back Det]
2
Scroll to Makeup gas type (or Makeup/reference gas type) and
press [Mode/Type].
3
Scroll to the correct gas and press [Enter].
Lit offset
The GC monitors the difference between the detector output
with the flame lit and the output when the flame is not lit.
If this difference falls below the setpoint, the GC assumes
that the flame has gone out and tries to reignite it. See “FID
automatic reignition (Lit offset)” on page 143 for details.
To configure the FPD heaters
The flame photometric detector (FPD) uses two heaters, one
in the base and one near the combustion chamber. When
configuring the FPD heaters, select Install Detector 2 htr rather
than the default Install Detector (FPD).
Advanced User Guide
31
3
Configuration
To ignore the FID or FPD ignitor
WA R N I N G
In general, do not ignore the ignitor for normal operation. Ignoring
the ignitor also disables the Lit Offset and autoignition features,
which work together to shut down the detector if the detector
flame goes out. If the flame goes out under manual ignition, GC
will continue to flow hydrogen fuel gas into the detector and lab.
Use this feature only if the ignitor is defective, and only until the
ignitor is repaired.
If using an FID or FPD, you can ignite the flame manually
by setting the GC to ignore the ignitor.
1 Press [Config][Front Det] or [Config][Back Det].
2
Scroll to Ignore Ignitor.
3
Press [On/Yes] to ignore the ignitor (or [Off/No] to enable
the ignitor.
When Ignore Ignitor is set to True, the GC does not try to light
the flame using the ignitor. The GC also completely ignores
the Lit Offset setpoint and does not attempt autoignition. This
means that the GC cannot determine if the flame is lit, and
will not shut down the fuel gas.
32
Advanced User Guide
Configuration
3
Analog Out
Fast peaks
The GC allows you to output analog data at two speeds. The
faster speed—to be used only with the FID, FPD, and
NPD—allows minimum peak widths of 0.004 minutes (8 Hz
bandwidth), while the standard speed—which can be used
with all detectors— allows minimum peak widths of 0.01
minutes (3.0 Hz bandwidth).
To use fast peaks:
1 Press [Config][[Analog Out 2].
2
Scroll to Fast peaks and press [On/Yes].
The fast peaks feature does not apply to digital output.
If you are using the fast peaks feature, your integrator must be
fast enough to process data coming from the GC. Integrator
bandwidth should be at least 15 Hz.
Advanced User Guide
33
3
Configuration
Valve Box
See “Unconfigured:” on page 25 and “Ignore Ready =” on
page 24.
The valve box mounts on top of the column oven. It may
contain up to two valves mounted on heated blocks. The
block can accommodate two valves.
Valve positions on the blocks are numbered. We suggest that
valves be installed in the blocks in numeric order.
All heated valves in a valve box are controlled by the same
temperature setpoint.
To assign a GC power source to a valve box heater
1 Unlock the GC configuration, press the [Options] key, select
Keyboard & Display and press the [Enter] key. Scroll down to
Hard Configuration Lock and press the [off] button.
2
Press [Config], scroll to Valve Box and press [Enter].
3
With Unconfigured selected, press [Mode/type], select one of
the following and press [Enter].
• Install heater A1 - for a valve box containing a single
heater plugged into the connector labeled A1 on the
valve box bracket.
• Install Heater A2 - for a valve box containing a single
heater plugged into the connector labeled A2 on the
valve box bracket.
The valve box bracket is located inside the GC right side
electrical compartment in the upper right location.
4
When prompted by the GC, turn the power off then on
again.
This completes the configuration of the valve box. To set the
valve box temperature for your method press the [valve #]
key, and scroll to Valve Box.
34
Advanced User Guide
3
Configuration
Thermal Aux
See “Unconfigured:” on page 25 and “Ignore Ready =” on
page 24.
The GC provides one additional channel of temperature
control, Thermal Aux 1.
To assign a GC power source to an Aux thermal zone
This procedure assigns the heater power source from heater
plug A1 to the Thermal Aux 1 temperature control zone.
1 Unlock the GC configuration, press [Options], select
Keyboard & Display and press [Enter]. Scroll down to Hard
Configuration Lock and press [Off/No].
2
Press [Config] and scroll to Thermal Aux 1.
3
With Unconfigured selected, press [Mode/Type], and select:
• Install Heater A1 if the heated device is plugged into the
valve box bracket plug labeled A1.
4
Press [Enter] after making selection.
5
When prompted by the GC, turn the power off then on
again.
To configure a MSD transfer line heater
1 Check that a power source for the MSD heater was
assigned. See “To assign a GC power source to an Aux
thermal zone” on page 35.
2
Press [Config] and scroll to Thermal Aux 1 or Back inlet
depending on where the MSD heater was assigned, and
press [Enter].
• For a single channel GC, select Back inlet.
• For a dual channel GC, select Thermal Aux 1.
3
Scroll to Auxiliary type, press [Mode/Type], scroll to and
select the MSD transfer line, and press [Enter].
To configure a nickel catalyst heater
1 Check that a power source for the Nickel Catalyst heater
was assigned. See “To assign a GC power source to an
Aux thermal zone” on page 35.
2
Advanced User Guide
Press [Config] and scroll to Back inlet, and press [Enter].
35
3
Configuration
3
36
Scroll to Auxiliary type, press [Mode/Type], scroll to and
select Nickel catalyst, and press [Enter].
Advanced User Guide
Configuration
3
PCM A/PCM B
See “Unconfigured:” on page 25 and “Ignore Ready =” on
page 24.
A pressure control module (PCM) provides one channel of
gas control.
This channel is a simple forward- pressure regulator that
maintains a constant pressure at its output. With a fixed
downstream restrictor, it provides constant flow.
To assign a GC communication source to a PCM
1 Unlock the GC configuration, press [Options], select
Keyboard & Display and press [Enter]. Scroll down to Hard
Configuration Lock and press [Off/No].
2
Press [Config], scroll to a PCMx and press [Enter].
3
With Unconfigured selected, press [Mode/Type], select Install
EPCx and press [Enter].
4
When prompted by the GC, turn the power off then on
again.
To configure the other parameters on this PCM, see To
configure a PCM.
To configure a PCM
1 Press [Config], scroll to the PCMx and press [Enter].
2
Scroll to Gas type, press [Mode/Type], make a selection and
press [Enter].
The pressure control mode is set by pressing [PCM #]. Select
Mode:, press [Mode/Type], select the mode and press [Enter].
Advanced User Guide
37
3
Configuration
Status
The [Status] key has two tables associated with it. You switch
between them by pressing the key.
The Ready/Not Ready status table
This table lists parameters that are Not Ready or gives you a
Ready for Injection display. If there are any faults, warnings, or
method mismatches present, they are displayed here.
The setpoint status table
This table lists setpoints compiled from the active parameter
lists on the instrument. This is a quick way to view active
setpoints during a run without having to open multiple lists.
To configure the setpoint status table
You can change the order of the list. You might want the
three most important setpoints to appear in the window
when you open the table.
1 Press [Config][Status].
38
2
Scroll to the setpoint that should appear first and press
[Enter]. This setpoint will now appear at the top of the
list.
3
Scroll to the setpoint that should appear second and
press [Enter]. This setpoint will now be the second item
on the list.
4
And so on, until the list is in the order you wish.
Advanced User Guide
Configuration
3
Time
Press [Time] to open this function. The first line always
displays the current date and time, and the last line always
displays a stopwatch. The two middle lines vary:
Between runs
During a run
run.
Show last and next (calculated) run times.
Show time elapsed and time remaining in the
During Post Run
time.
Show last run time and remaining Post Run
To set time and date
1 Press [Config][Time].
2
Select Time zone (hhmm) and enter the local time offset
from GMT using a 24 hour format.
3
Select Time (hhmm) and enter the local time.
4
Select Date (ddmmyy) and enter the date.
To use the stopwatch
1 Press [Time].
Advanced User Guide
2
Scroll to the time= line.
3
To begin the timed period press [Enter].
4
To stop the timed period press [Enter].
5
Press [Clear] to reset the stopwatch.
39
3
Configuration
Valve #
Up to 2 valves can be mounted in a temperature- controlled
valve box.
To configure a valve
1 Press [Config][Valve #] and enter the number of the valve
you are configuring. The current valve type is displayed.
2
To change the valve type, press [Mode/Type], select the
new valve type, and press [Enter].
Valve types
• Sampling Two- position (load and inject) valve. In load
position, an external sample stream flows through an
attached (gas sampling) or internal (liquid sampling) loop
and out to waste. In inject position, the filled sampling
loop is inserted into the carrier gas stream. When the
valve switches from Load to Inject, a run starts if one is
not already in progress. See the example in “Gas sampling
valve” on page 183.
• Not installed
40
Self- explanatory.
Advanced User Guide
Configuration
3
Front injector/Back injector
The injectors are normally plugged into the Front ALS Port on
the GC when used for injections into the front inlet, and the
Back ALS Port on the GC when used for injections into the
back inlet.
To configure the 7693A sampler system, see the 7693A
Installation, Operation, and Maintenance manual.
Advanced User Guide
41
3
Configuration
Instrument
1 Press [Config]. Scroll to Instrument and press [Enter].
2
Scroll to Serial #. Enter a serial number and press [Enter].
This function can only be done by Agilent service
personnel.
3
Scroll to Auto prep run. Press [On/Yes] to enable Auto prep
run, [Off/No] to disable it. See “Pre Run and Prep Run” on
page 110 for details.
4
Scroll to Zero Init Data Files.
• Press [On/Yes] to enable it. When it is On, the GC
immediately begins to subtract the current detector
output from all future values. This applies only to
digital output, and is useful when a non- Agilent data
system has problems with baseline data that is
non- zero.
• Press [Off/No] to disable it. This is appropriate for all
Agilent data systems.
42
5
The Oven line displays the GC power configuration.
6
Press [Clear] to return to the Config menu or any other
function to end.
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
4
Options
About Options 44
Calibration 45
Maintaining EPC calibration—inlets, detectors, and PCM 45
Auto flow zero 45
Zero conditions 46
Zero intervals 46
To zero a specific flow or pressure sensor 46
To zero all pressure sensors in all modules 47
Column calibration 47
Communication 51
Configuring the IP address for the GC 51
Keyboard and Display 52
Agilent Technologies
43
4
Options
About Options
The [Options] key is used for a group of functions that are
usually set on installation and seldom changed afterward. It
accesses this menu:
Calibration
Communication
Keyboard and Display
44
Advanced User Guide
Options
4
Calibration
Press [Calibration] to list the parameters that can be
calibrated. These include:
• Inlets
• Detectors
• ALS
• Columns
• Oven
• Atmospheric pressure
In general, you will only need to calibrate the EPC modules
and capillary columns. ALS, oven, and atmospheric pressure
calibration should only be performed be trained service
personnel.
The calibration displays are discussed in the Agilent 7820A
Service Manual.
Maintaining EPC calibration—inlets, detectors, and PCM
The EPC gas control modules contain flow and/or pressure
sensors that are calibrated at the factory. Sensitivity (slope
of the curve) is quite stable, but zero offset requires periodic
updating.
Flow sensors
The split/splitless and purged packed inlet modules use flow
sensors. If the Auto flow zero feature (see page 45) is on, they
are zeroed automatically after each run. This is the
recommended way. They can also be zeroed manually—see
“To zero a specific flow or pressure sensor.
Pressure sensors
All EPC control modules use pressure sensors. They can be
zeroed as a group or individually. There is no automatic zero
for pressure sensors.
Auto flow zero
A useful calibration option is Auto flow zero. When it is On,
after the end of a run the GC shuts down the flow of gases
to an inlet, waits for the flow to drop to zero, measures and
Advanced User Guide
45
4
Options
stores the flow sensor output, and turns the gas back on.
This takes about two seconds. The zero offset is used to
correct future flow measurements.
To activate this, select Calibration on the Options menu, then
choose either Front inlet or Back inlet, press [Enter], and turn
Auto flow zero on.
Zero conditions
Flow sensors are zeroed with the carrier gas connected and
flowing.
Pressure sensors are zeroed with the supply gas line
disconnected from the gas control module.
Zero intervals
Table 1
Flow and Pressure Sensor Zero Intervals
Sensor type
Module type
Zero interval
Flow
All
Use Auto flow zero and/or
Auto zero septum purge
Pressure
Inlets
Packed columns
Every 12 months
Small capillary columns
(id 0.32 mm or less)
Every 12 months
Large capillary columns
(id > 0.32 mm)
At 3 months, at 6 months,
then every 12 months
Auxiliary channels
Every 12 months
Detector gases
Every 12 months
To zero a specific flow or pressure sensor
1 Press [Options], scroll to Calibration, and press [Enter].
2
Scroll to the module to be zeroed and press [Enter].
3
Scroll to a zero line and press [Info]. The GC will remind
you of the conditions necessary for zeroing that specific
sensor.
Flow sensors. Verify that the gas is connected and
flowing (turned on).
Pressure sensors. Disconnect the gas supply line at the
back of the GC. Turning it off is not adequate; the valve
may leak.
46
Advanced User Guide
4
Options
4
Press [On/Yes] to zero or [Clear] to cancel.
To zero all pressure sensors in all modules
1 Press [Service Mode], scroll to Diagnostics, and press [Enter].
2
Scroll to Electronics and press [Enter].
3
Scroll to Pneumatics and press [Enter].
4
Scroll to Zero all pressure sensors and press [Info]. The GC
will remind you that all gas supplies must be
disconnected at the back panel. Turning them off is not
adequate; the valves may leak.
5
Press [On/Yes] to zero or [Clear] to cancel.
Column calibration
As you use a capillary column, you may occasionally trim off
portions, changing the column length. If measuring the
actual length is impractical, and if you are using EPC with a
defined column, you can use an internal calibration routine
to estimate the actual column length. Similarly, if you do not
know the column internal diameter or believe it is
inaccurate, you can estimate the diameter from related
measurements.
Before you can calibrate the column, make sure that:
• You are using a capillary column
• The column is defined
• There are no oven ramps
• The column gas source (usually the inlet) is On and
non- zero
Also note that column calibration fails if the calculated
column length correction is > 5 m, or if the calculated
diameter correction is > 20 μm.
Calibration modes
There are three ways to calibrate the column length and/or
diameter:
• Calibrate using an actual measured column flow rate
• Calibrate using an unretained peak time (elution time)
• Calibrate both length and diameter using flow rate and
elution time
Advanced User Guide
47
4
Options
CAUTION
When you measure the column flow rate, be sure to convert the
measurement to normal temperature and pressure if your
measurement device does not report data at NTP. If you enter
uncorrected data, the calibration will be wrong.
To estimate the actual column length or diameter from an elution
time
1 Set oven ramp 1 to 0.00, then verify that the column is
defined.
2
Perform a run using an unretained compound and record
the elution time.
3
Press [Options], scroll to Calibration and press [Enter].
4
From the calibration list, select the column and press
[Enter]. The GC displays the current calibration mode for
the column.
5
To recalibrate or to change calibration mode, press
[Mode/Type] to see the column calibration mode menu.
6
Scroll to Length or Diameter and press [Enter]. The
following choices appear:
• Mode
• Measured flow
• Unretained peak
• Calculated length or Calculated diameter
• Not calibrated
7
Scroll to Unretained peak and enter the actual elution time
from the run performed above.
8
When you press [Enter], the GC will estimate the column
length or diameter based on the elution time input and
will now use that data for all calculations.
To estimate the actual column length or diameter from the
measured flow rate
1 Set oven ramp 1 to 0.00, then verify that the column is
defined.
48
2
Set the oven, inlet, and detectors temperatures to 35 °C
and allow them to cool to room temperature.
3
Remove the column from the detector.
Advanced User Guide
4
Options
CAUTION
When you measure the column flow rate, be sure to convert the
measurement to normal temperature and pressure if your
measurement device does not report data at NTP. If you enter
uncorrected data, the calibration will be wrong.
4
Measure the actual flow rate through the column using a
bubble meter. Record the value. Reinstall the column.
5
Press [Options], scroll to Calibration and press [Enter].
6
From the calibration list, select the column and press
[Enter]. The GC displays the current calibration mode for
the column.
7
To recalibrate or to change calibration mode, press
[Mode/Type] to see the column calibration mode menu.
8
Scroll to Length or Diameter and press [Enter]. The
following choices appear:
• Mode
• Measured flow
• Unretained peak
• Calculated length or Calculated diameter
• Not calibrated
9
Scroll to Measured flow and enter the corrected column
flow rate (in mL min) from the run performed above.
10 When you press [Enter], the GC will estimate the column
length or diameter based on the elution time input and
will now use that data for all calculations.
To estimate the actual column length and diameter
1 Set oven ramp 1 to 0.00, then verify that the column is
defined.
Advanced User Guide
2
Perform a run using an unretained compound and record
the elution time.
3
Set the oven, inlet, and detectors temperatures to 35 °C
and allow them to cool to room temperature.
4
Remove the column from the detector.
49
4
Options
CAUTION
When you measure the column flow rate, be sure to convert the
measurement to normal temperature and pressure if your
measurement device does not report data at NTP. If you enter
uncorrected data, the calibration will be wrong.
5
Measure the actual flow rate through the column using a
bubble meter. Record the value. Reinstall the column.
6
Press [Options], scroll to Calibration and press [Enter].
7
From the calibration list, select the column and press
[Enter]. The GC displays the current calibration mode for
the column.
8
To recalibrate or to change calibration mode, press
[Mode/Type] to see the column calibration mode menu.
9
Scroll to Length & diameter and press [Enter]. The following
choices appear:
• Mode
• Measured flow
• Unretained peak
• Calculated length
• Calculated diameter
• Not calibrated
10 Scroll to Measured flow and enter the corrected column
flow rate (in mL min) from the run performed above.
11 Scroll to Unretained peak and enter the actual elution time
from the run performed above.
12 When you press [Enter], the GC will estimate the column
length or diameter based on the elution time input and
will now use that data for all calculations.
50
Advanced User Guide
4
Options
Communication
Configuring the IP address for the GC
For network (LAN) operation, the GC needs an IP address. It
can get this from a DHCP server, or it can be entered
directly from the keyboard. In either case, see your LAN
administrator.
To use a DHCP server
1 Press [Options]. Scroll to Communications and press [Enter].
2
Scroll to Enable DHCP and press [On/Yes]. When prompted,
turn the GC off and then on again.
To set the LAN address at the keyboard
1 Press [Options]. Scroll to Communications and press [Enter].
Advanced User Guide
2
Scroll to Enable DHCP and, if necessary, press [Off/No].
Scroll to Reboot GC. Press [On/Yes] and [On/Yes].
3
Press [Options]. Scroll to Communications and press [Enter].
4
Scroll to IP. Enter the numbers of the GC IP address,
separated by dots, and press [Enter]. A message tells you
to power cycle the instrument. Do not power cycle yet.
Press [Clear].
5
Scroll to GW. Enter the Gateway number and press
[Enter]. A message tells you to power cycle the
instrument. Do not power cycle yet. Press [Clear].
6
Scroll to SM and press [Mode/Type]. Scroll to the
appropriate subnet mask from the list given and press
[Enter]. A message tells you to power cycle the
instrument. Do not power cycle yet. Press [Clear].
7
Scroll to Reboot GC. Press [On/Yes] and [On/Yes] to power
cycle the instrument and apply the LAN setpoints.
51
4
Options
Keyboard and Display
Press [Options] and scroll to Keyboard and Display. Press
[Mode/Type].
The following parameters are turned on and off by pressing
the [On/Yes] or [Off/No] keys.
Keyboard lock These keys and functions are operational
when the keyboard lock is On:
[Start], [Stop], and [Prep Run]
[Load][Method] and [Load][Seq]
[Seq]—to edit existing sequences
[Seq Control]—to start or stop sequences.
Hard configuration lock On prevents keyboard configuration
changes; Off removes lock.
Key click
Click sound when keys are pressed.
Warning beep
Allows you to hear warning beeps.
Warning beep mode There are 9 different warning sounds
that may be selected. This allows you to give multiple GCs
individual “voices”. We suggest you experiment.
Method modified beep Turn on for high pitched beep when
method setpoint is modified.
Press [Mode/Type] to change the pressure units and radix
type.
Pressure units
psi—pounds per square inch, lb/in2
bar—absolute cgs unit of pressure, dyne/cm2
kPa—mks unit of pressure, 103 N/m2
Language
Radix type
1,00
Select English or Chinese or Japanese.
Determines the numeric separator type—1.00 or
Display saver If On, dims the display after a period of
inactivity. If Off, disabled.
52
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
5
Chromatographic Checkout
About Chromatographic Checkout 54
To Prepare for Chromatographic Checkout 55
To Check FID Performance 56
To Check TCD Performance 60
To Check NPD Performance 64
To Check uECD Performance 68
To Check FPD Performance (Sample 5188-5953) 72
Agilent Technologies
53
5
Chromatographic Checkout
About Chromatographic Checkout
The tests described in this section provide basic
confirmation that the GC and detector can perform
comparably to factory condition. However, as detectors and
the other parts of the GC age, detector performance can
change. The results presented here represent typical outputs
for typical operating conditions and are not specifications.
The tests assume the following:
• Use of an automatic liquid sampler. If not available, use a
suitable manual syringe instead of the syringe listed.
• Use of a 10- µL syringe in most cases. However, a 5- µL
syringe is an acceptable substitute for the 1- µL injections
described here.
• Use of the septa and other hardware (liners, jets,
adapters, and so forth) described. If you substitute other
hardware, performance can vary.
Selected tests described in this section can be run
automatically using the documentation and utility DVD
provided with your GC.
54
Advanced User Guide
5
Chromatographic Checkout
To Prepare for Chromatographic Checkout
Because of the differences in chromatographic performance
associated with different consumables, Agilent strongly
recommends using the parts listed here for all checkout
tests. Agilent also recommends installing new consumable
parts whenever the quality of the installed ones is not
known. For example, installing a new liner and septum
ensures that they will not contribute any contamination to
the results.
1 Check the indicators/dates on any gas supply traps.
Replace/recondition expended traps.
2
Install new consumable parts for the inlet and prepare
the correct injector syringe (and needle, as needed).
Table 2
Recommended parts for checkout by inlet type
Recommended part for checkout
Part number
Split splitless inlet
Syringe, 10-µL
5181-1267
O-ring
5188-5365
Septum
5183-4757
Liner
5062-3587 or 5181-3316
Packed column inlet
Advanced User Guide
Syringe, 10-µL
5181-1267
O-ring
5080-8898
Septum
5183-4757
55
5
Chromatographic Checkout
To Check FID Performance
1 Gather the following:
• Evaluation column, HP- 5 30 m × 0.32 mm × 0.25 µm
(19091J- 413)
• FID performance evaluation (checkout) sample
(5188- 5372)
• Chromatographic- grade isooctane
• 4- mL solvent and waste bottles or equivalent for
autoinjector
• 2- mL sample vials or equivalent for sample
• Inlet and injector hardware (See “To Prepare for
Chromatographic Checkout.”)
2
Verify the following:
• Capillary column jet installed. If not, select and install
a capillary column jet.
• Capillary column adapter installed (adaptable FID
only). If not, install it.
• Chromatographic- grade gases plumbed and configured:
helium as carrier gas, nitrogen, hydrogen, and air.
(Nitrogen is an acceptable alternate carrier gas.)
• Empty waste vials loaded in sample turret.
• 4- mL solvent vial with diffusion cap filled with
isooctane and inserted in Solvent A injector position.
3
Replace consumable parts (liner, septum, traps, syringe,
and so forth) as needed for the checkout. See “To Prepare
for Chromatographic Checkout.”
4
Install the evaluation column. (See the procedure for the
SS or PP in the Maintenance manual.)
• Bake out the evaluation column for at least 30 min at
180 °C. (See the procedure for the SS, or PP in the
Maintenance manual.)
• Be sure to configure the column.
5
Check the FID baseline output. The output should be
between 5 pA and 20 pA and relatively stable. (If using a
gas generator or ultra pure gas, the signal may stabilize
below 5 pA.) If the output is outside this range or
unstable, resolve this problem before continuing.
6
If the output is too low:
• Check that the electrometer is on.
56
Advanced User Guide
Chromatographic Checkout
5
• Check that the flame is lit (“To light the FID flame” on
page 143).
7
Create or load a method with the parameter values listed
in Table 3.
Table 3
FID Checkout Conditions
Column and sample
Type
HP-5, 30 m × 0.32 mm × 0.25 µm
(19091J-413)
Sample
FID checkout 5188-5372
Column flow
6.5 mL/min
Column mode
Constant flow
Split/splitless inlet
Temperature
250 °C
Mode
Splitless
Purge flow
40 mL/min
Purge time
0.5 min
Gas saver
Off
Packed column inlet
Temperature
250 °C
Detector
Temperature
300 °C
H2 flow
30 mL/min
Air flow
400 mL/min
Makeup flow (N2)
25 mL/min
Lit offset
Typically 2 pA
Oven
Initial temp
75 °C
Initial time
0.5 min
Rate 1
20 °C/min
Final temp
190 °C
Final time
0 min
ALS settings (if installed)
Advanced User Guide
57
5
Chromatographic Checkout
Table 3
FID Checkout Conditions (continued)
Sample washes
2
Sample pumps
6
Sample wash volume
8
Injection volume
1 µL
Syringe size
10 µL
Solvent A pre washes
2
Solvent A post washes
2
Solvent A wash volume
8
Solvent B pre washes
0
Solvent B post washes
0
Solvent B wash volume
0
Injection mode
Normal
Airgap Volume
0.20
Viscosity delay
0
Inject Dispense Speed (7693A)
6000
PreInjection dwell
0
PostInjection dwell
0
Manual injection
Injection volume
1 µL
Data system
Data rate
8
5 Hz
If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
If not using a data system, create a one sample sequence
using the GC keypad.
9
Start the run.
If performing an injection using an autosampler, start the
run using the data system or press [Start] on the GC.
58
Advanced User Guide
Chromatographic Checkout
5
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
10 The following chromatogram shows typical results for a
new detector with new consumable parts installed and
nitrogen makeup gas.
FID1 A, (C:\FID.D)
C15
pA
400
C16
350
300
250
200
150
100
C13
50
C14
0
0
1
Advanced User Guide
2
3
4
5
min
59
5
Chromatographic Checkout
To Check TCD Performance
1 Gather the following:
• Evaluation column, HP- 5 30 m × 0.32 mm × 0.25 µm
(19091J- 413)
• FID/TCD performance evaluation (checkout) sample
(18710- 60170)
• 4- mL solvent and waste bottles or equivalent for
autoinjector
• Chromatographic- grade hexane
• 2- mL sample vials or equivalent for sample
• Chromatographic- grade helium as carrier, makeup, and
reference gas
• Inlet and injector hardware (See “To Prepare for
Chromatographic Checkout.”)
2
Verify the following:
• Chromatographic- grade gases plumbed and configured:
helium as carrier gas and reference gas.
• Empty waste vials loaded in sample turret.
• 4- mL solvent vial with diffusion cap filled with hexane
and inserted in Solvent A injector position.
3
Replace consumable parts (liner, septum, traps, syringe,
and so forth) as needed for the checkout. See “To Prepare
for Chromatographic Checkout.”
4
Install the evaluation column. (See the procedure for the
SS or PP in the Maintenance manual.)
• Bake out the evaluation column for at least 30 min at
180 °C. (See the procedure for the SS or PP in the
Maintenance manual.)
• Configure the column
5
Create or load a method with the parameter values listed
in Table 4.
Table 4
TCD Checkout Conditions
Column and sample
60
Type
HP-5, 30 m × 0.32 mm × 0.25 µm
(19091J-413)
Sample
FID/TCD checkout 18710-60170
Advanced User Guide
Chromatographic Checkout
Table 4
5
TCD Checkout Conditions (continued)
Column flow
6.5 mL/min
Column mode
Constant flow
Split/splitless inlet
Temperature
250 °C
Mode
Splitless
Purge flow
60 mL/min
Purge time
0.75 min
Packed column inlet
Temperature
250 °C
Detector
Temperature
300 °C
Reference flow (He)
20 mL/min
Makeup flow (He)
2 mL/min
Baseline output
< 30 display counts on Agilent
ChemStation (< 750 µV)
Oven
Initial temp
40 °C
Initial time
0 min
Rate 1
20 °C/min
Final temp
90 °C
Final time
0 min
Rate 2
15 °C/min
Final temp
170 °C
Final time
0 min
ALS settings (if installed)
Advanced User Guide
Sample washes
2
Sample pumps
6
Sample wash volume
8
Injection volume
1 µL
Syringe size
10 µL
Solvent A pre washes
2
Solvent A post washes
2
61
5
Chromatographic Checkout
Table 4
TCD Checkout Conditions (continued)
Solvent A wash volume
8
Solvent B pre washes
0
Solvent B post washes
0
Solvent B wash volume
0
Injection mode
Normal
Airgap Volume
0.20
Viscosity delay
0
Inject Dispense Speed (7693A)
6000
PreInjection dwell
0
PostInjection dwell
0
Manual injection
Injection volume
1 µL
Data system
Data rate
6
5 Hz
Display the signal output. A stable output at any value
between 12.5 and 750 µV (inclusive) is acceptable.
• If the baseline output is < 0.5 display units (< 12.5 µV),
verify that the detector filament is on. If the offset is
still < 0.5 display units (< 12.5 µV), your detector
requires service.
• If baseline output is > 30 display units (> 750 µV),
there may be chemical contamination contributing to
the signal. Bakeout the TCD. If repeated cleanings do
not give an acceptable signal, check gas purity. Use
higher purity gases and/or install traps.
7
If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
8
Start the run.
If performing an injection using an autosampler, start the
run using the data system or press [Start] on the GC.
62
Advanced User Guide
Chromatographic Checkout
5
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
9
The following chromatogram shows typical results for a
new detector with new consumable parts installed.
25 uV
70
C14
C15
C16
60
50
40
30
20
2
4
6
8
Time (min.)
Advanced User Guide
63
5
Chromatographic Checkout
To Check NPD Performance
1 Gather the following:
• Evaluation column, HP- 5 30 m × 0.32 mm × 0.25 µm
(19091J- 413)
• NPD performance evaluation (checkout) sample
(18789- 60060)
• 4- mL solvent and waste bottles or equivalent for
autoinjector.
• Chromatographic- grade isooctane
• 2- mL sample vials or equivalent for sample.
• Inlet and injector hardware (See “To Prepare for
Chromatographic Checkout.”)
2
Verify the following:
• Capillary column jet installed. If not, select and install
a capillary column jet.
• Capillary column adapter installed. If not, install it.
• Chromatographic- grade gases plumbed and configured:
helium as carrier gas, nitrogen, hydrogen, and air.
• Empty waste vials loaded in sample turret.
• 4- mL vial with diffusion cap filled with isooctane and
inserted in Solvent A injector position.
3
Replace consumable parts (liner, septum, traps, syringe,
and so forth) as needed for the checkout. See “To Prepare
for Chromatographic Checkout.”
4
If present, remove any protective caps from the inlet
manifold vents.
5
Install the evaluation column. (See the procedure for the
SS or PP in the Maintenance manual.)
• Bake out the evaluation column for at least 30 min at
180 °C. (See the procedure for the SS or PP in the
Maintenance manual.)
• Be sure to configure the column
6
64
Create or load a method with the parameter values listed
in Table 5.
Advanced User Guide
Chromatographic Checkout
Table 5
5
NPD Checkout Conditions
Column and sample
Type
HP-5, 30 m × 0.32 mm × 0.25 µm
(19091J-413)
Sample
NPD checkout 18789-60060
Column mode
Constant flow
Column flow
6.5 mL/min (helium)
Split/splitless inlet
Temperature
200 °C
Mode
Splitless
Purge flow
60 mL/min
Purge time
0.75 min
Packed column inlet
Temperature
200 °C
Detector
Temperature
300 °C
H2 flow
3 mL/min
Air flow
60 mL/min
Makeup flow (N2)
Makeup + column = 10 mL/min
Output
30 display units (30 pA)
Oven
Initial temp
60 °C
Initial time
0 min
Rate 1
20 °C/min
Final temp
200 °C
Final time
3 min
ALS settings (if installed)
Advanced User Guide
Sample washes
2
Sample pumps
6
Sample wash volume
8
Injection volume
1 µL
65
5
Chromatographic Checkout
Table 5
NPD Checkout Conditions (continued)
Syringe size
10 µL
Solvent A pre washes
2
Solvent A post washes
2
Solvent A wash volume
8
Solvent B pre washes
0
Solvent B post washes
0
Solvent B wash volume
0
Injection mode
Normal
Airgap Volume
0.20
Viscosity delay
0
Inject Dispense Speed (7693A)
6000
PreInjection dwell
0
PostInjection dwell
0
Manual injection
Injection volume
1 µL
Data system
Data rate
5 Hz
7
If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
8
Start the run.
If performing an injection using an autosampler, start the
run using the data system, or creating a one sample
sequence and pressing [Start] on the GC.
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
9
66
The following chromatogram shows typical results for a
new detector with new consumable parts installed.
Advanced User Guide
Chromatographic Checkout
NPD1 B, (C:\NPD.D)
5
Malathion
pA
70
60
Azobenzene
50
40
30
20
Octadecane
10
1
Advanced User Guide
2
3
4
5
6
7
8
9
m
67
5
Chromatographic Checkout
To Check uECD Performance
1 Gather the following:
• Evaluation column, HP- 5 30 m × 0.32 mm × 0.25 µm
(19091J- 413)
• uECD performance evaluation (checkout) sample
(18713–60040, Japan: 5183- 0379)
• 4- mL solvent and waste bottles or equivalent for
autoinjector.
• Chromatographic- grade isooctane
• 2- mL sample vials or equivalent for sample.
• Inlet and injector hardware (See “To Prepare for
Chromatographic Checkout.”)
2
Verify the following:
• Clean fused silica indented mixing liner installed. If
not, install it.
• Chromatographic- grade gases plumbed and configured:
helium for carrier gas, nitrogen for makeup. (Nitrogen
is an acceptable alternate carrier gas.)
• Empty waste vials loaded in sample turret.
• 4- mL vial with diffusion cap filled with hexane and
inserted in Solvent A injector position.
3
Replace consumable parts (liner, septum, traps, syringe,
and so forth) as needed for the checkout. See “To Prepare
for Chromatographic Checkout.”
4
Install the evaluation column. (See the procedure for the
SS or PP in the Maintenance manual.)
• Bake out the evaluation column for at least 30 minutes
at 180 °C. (See the procedure for the SS or PP in the
Maintenance manual.)
• Be sure to configure the column.
5
Display the signal output to determine baseline output. A
stable baseline output at any value between 0.5 and
1000 Hz (ChemStation display units) (inclusive) is
acceptable.
• If the baseline output is < 0.5 Hz, verify that the
electrometer is on. If the offset is still < 0.5 Hz, your
detector requires service.
68
Advanced User Guide
Chromatographic Checkout
5
• If the baseline output is > 1000 Hz, there may be
chemical contamination contributing to the signal.
Bakeout the uECD. If repeated cleanings do not give an
acceptable signal, check gas purity. Use higher purity
gases and/or install traps.
6
Create or load a method with the parameter values listed
in Table 6.
Table 6
uECD Checkout Conditions
Column and sample
Type
HP-5, 30 m × 0.32 mm × 0.25 µm
(19091J-413
Sample
µECD checkout (18713-60040 or Japan:
5183-0379)
Column mode
Constant flow
Column flow
6.5 mL/min (helium)
Split/splitless inlet
Temperature
200 °C
Mode
Splitless
Purge flow
60 mL/min
Purge time
0.75 min
Packed column inlet
Temperature
200 °C
Detector
Temperature
300 °C
Makeup flow (N2)
30 mL/min (constant + makeup)
Baseline output
Should be < 1000 display counts in
Agilent ChemStation (< 1000 Hz)
Oven
Initial temp
80 °C
Initial time
0 min
Rate 1
15 °C/min
Final temp
180 °C
Final time
10 min
ALS settings (if installed)
Advanced User Guide
69
5
Chromatographic Checkout
Table 6
uECD Checkout Conditions (continued)
Sample washes
2
Sample pumps
6
Sample wash volume
8
Injection volume
1 µL
Syringe size
10 µL
Solvent A pre washes
2
Solvent A post washes
2
Solvent A wash volume
8
Solvent B pre washes
0
Solvent B post washes
0
Solvent B wash volume
0
Injection mode
Normal
Airgap Volume
0.20
Viscosity delay
0
Inject Dispense Speed (7693A)
6000
PreInjection dwell
0
PostInjection dwell
0
Manual injection
Injection volume
1 µL
Data system
Data rate
5 Hz
7
If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
8
Start the run.
If performing an injection using an autosampler, start the
run using the data system or press [Start] on the GC.
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
70
Advanced User Guide
Chromatographic Checkout
9
5
The following chromatogram shows typical results for a
new detector with new consumable parts installed.
ECD1 B, (C:\ECD.D)
Hz
Lindane
(18713-60040
5183-0379)
12000
10000
8000
Aldrin
(18713-60040)
6000
4000
2000
0
2
Advanced User Guide
4
6
8
10
12 min
71
5
Chromatographic Checkout
To Check FPD Performance (Sample 5188-5953)
To check FPD performance, first check the phosphorus
performance, then the sulfur performance.
Preparation
1 Gather the following:
• Evaluation column, HP- 5 30 m × 0.32 mm × 0.25 µm
(19091J- 413)
• FPD performance evaluation (checkout) sample
(5188- 5953), 2.5 mg/L (± 0.5%) methylparathion in
isooctane
• Phosphorus filter
• Sulfur filter and filter spacer
• 4- mL solvent and waste bottles or equivalent for
autoinjector.
• 2- mL sample vials or equivalent for sample.
• Chromatographic- grade isooctane for syringe wash
solvent.
• Inlet and injector hardware (See “To Prepare for
Chromatographic Checkout.”)
2
Verify the following:
• Capillary column adapter installed. If not, install it.
• Chromatographic- grade gases plumbed and configured:
helium as carrier gas, nitrogen, hydrogen, and air.
• Empty waste vials loaded in sample turret.
• 4- mL vial with diffusion cap filled with isooctane and
inserted in Solvent A injector position.
3
Replace consumable parts (liner, septum, traps, syringe,
and so forth) as needed for the checkout. See “To Prepare
for Chromatographic Checkout.”
4
Verify that the Lit Offset is set appropriately. Typically, it
should be about 2.0 pA for the checkout method.
5
Install the evaluation column. (See the procedure for the
SS or PP in the Maintenance manual.)
• Set the oven, inlet, and detector to 250 °C and bake
out for at least 15 minutes. (See the procedure for the
SS or PP in the Maintenance manual.)
• Be sure to configure the column.
72
Advanced User Guide
Chromatographic Checkout
5
Phosphorus performance
6
If it is not already installed, install the phosphorus filter.
7
Create or load a method with the parameter values listed
in Table 7.
Table 7
FPD Checkout Conditions (P)
Column and sample
Type
HP-5, 30 m × 0.32 mm × 0.25 µm
(19091J-413)
Sample
FPD checkout (5188-5953)
Column mode
Constant pressure
Column pressure
25 psi
Split/splitless inlet
Temperature
200 °C Split/splitless
Mode
Splitless
Purge flow
60 mL/min
Purge time
0.75 min
Packed column inlet
Temperature
200 °C
Detector
Temperature
200 °C (On)
Hydrogen flow
75 mL/min (On)
Air (Oxidizer) flow
100 mL/min (On)
Mode
Constant makeup flow OFF
Makeup flow
60 mL/min (On)
Makeup gas type
Nitrogen
Flame
On
Lit offset
Typically 2 pA
High voltage
On
Oven
Advanced User Guide
Initial temp
70 °C
Initial time
0 min
Rate 1
25 °C/min
73
5
Chromatographic Checkout
Table 7
FPD Checkout Conditions (continued)(P)
Final temp 1
150 °C
Final time 1
0 min
Rate 2
5 °C/min
Final temp 2
190 °C
Final time 2
4 min
ALS settings (if installed)
Sample washes
2
Sample pumps
6
Sample wash volume
8
Injection volume
1 µL
Syringe size
10 µL
Solvent A pre washes
2
Solvent A post washes
2
Solvent A wash volume
8
Solvent B pre washes
0
Solvent B post washes
0
Solvent B wash volume
0
Injection mode
Normal
Airgap Volume
0.20
Viscosity delay
0
Inject Dispense Speed (7693A)
6000
PreInjection dwell
0
PostInjection dwell
0
Manual injection
Injection volume
1 µL
Data system
Data rate
74
5 Hz
8
Ignite the FPD flame, if not lit.
9
Display the signal output and monitor. This output
typically runs between 40 and 55 but can be as high as
70. Wait for the output to level off. This takes
approximately 1 hour.
Advanced User Guide
Chromatographic Checkout
5
If the baseline output is too high:
• Check column installation. If installed high, the
stationery phase burns out and increases measured
output.
• Check for leaks.
• Bake out the detector and column at 250 °C.
• Wrong flows set for installed filter.
If the baseline output is zero, verify the electrometer is on
and the flame is lit.
10 If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
11 Start the run.
If performing an injection using an autosampler, start the
run using the data system or press [Start] on the GC.
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
12 The following chromatogram shows typical results for a
new detector with new consumable parts installed.
Advanced User Guide
75
5
Chromatographic Checkout
Methylparathion
Isooctane
Sulfur performance
13 Install the sulfur filter and filter spacer.
14 Make the following method parameter changes.
Table 8
Sulfur method parameters (S)
Parameter
Value ( mL/min)
H2 flow
50
Air flow
60
15 Ignite the FPD flame if not lit.
16 Display the signal output and monitor. This output
typically runs between 50 and 60 but can be as high as
70. Wait for the output to level off. This takes
approximately 1 hour.
If the baseline output is too high:
• Check column installation. If installed high, the
stationery phase burns out and increases measured
output.
• Check for leaks.
• Bake out the detector and column at 250 °C.
• Wrong flows set for installed filter.
76
Advanced User Guide
Chromatographic Checkout
5
If the baseline output is zero, verify the electrometer is on
and the flame is lit.
17 If using a data system, prepare the data system to
perform one run using the loaded checkout method. Make
sure that the data system will output a chromatogram.
18 Start the run.
If performing an injection using an autosampler, start the
run using the data system or press [Start] on the GC.
If performing a manual injection (with or without a data
system):
a Press [Prep Run] to prepare the inlet for splitless
injection.
b When the GC becomes ready, inject 1 µL of the
checkout sample and press [Start] on the GC.
19 The following chromatogram shows typical results for a
new detector with new consumable parts installed.
Methylparathion
Isooctane
Advanced User Guide
77
5
78
Chromatographic Checkout
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
6
Methods and Sequences
Creating Methods 80
To program a method 80
To program the ALS 81
To save a method 81
To load a stored method 81
Method mismatch 81
Creating Sequences 83
About the priority sequence 83
To program a sequence 83
To program a priority sequence 84
To program an ALS subsequence 85
To program a valve subsequence 85
To program post sequence events 85
To save a sequence 86
To load a stored sequence 86
To determine sequence status 86
To start a sequence 86
To pause and resume a sequence 87
To stop a sequence 87
To abort a sequence 87
Agilent Technologies
79
6
Methods and Sequences
Creating Methods
A method is the group of setpoints needed to run a single
sample on the GC, such as oven temperature programs,
pressure programs, inlet temperatures, sampler parameters,
etc. A method is created by saving a group of setpoints as a
numbered method using the [Store] key.
Components for which setpoint parameters can be stored are
shown in Table 9.
Table 9
Setpoint parameter components
Component
Component
Oven
Analog Out
Valve 1–2
Front and back injector (see the ALS
operating manual)
Front and back inlet
Aux temp
Columns 1 to 4
Post run
Front and back detector
Run table
The GC also saves ALS setpoints. See the 7693A Installation,
Operation, and Maintenance manual for details on its
setpoints.
Setpoint parameters are saved when the GC is turned off
and loaded when you turn the instrument back on. However,
if the hardware was changed while the instrument was
turned off, it may not be possible to restore all setpoints in
the method.
To program a method
1 Individually select each component for which setpoint
parameters are appropriate for your method. (See
Table 9.)
80
2
Examine the current setpoints and modify as desired.
Repeat for each component as appropriate.
3
Examine the current setpoints for the ALS, if
appropriate, and modify as desired. (See “To program the
ALS” on page 81.)
Advanced User Guide
6
Methods and Sequences
Save the setpoints as a stored method. (See “To save a
method” on page 81.)
4
To program the ALS
1 Press [Front Injector] or [Back Injector].
2
Scroll to the desired setpoint.
3
Enter a setpoint value.
4
Save the setpoints as a stored method. (See “To save a
method” on page 81.)
To save a method
1 Press [Method] and scroll to the desired method number.
2
Press [Store] and [On/Yes] to store the new method using
the chosen number. Alternatively, press [Off/No] to return
to the stored methods list without saving the method.
A message is displayed if a method with the number you
selected already exists.
• Press [On/Yes] to replace the existing method or
[Off/No] to return to the stored methods list without
saving the method.
To load a stored method
Press [Load][Method]. Supply the method number and press
[Enter]. The specified method will replace the current active
method.
Method mismatch
This section applies only to a standalone (not connected to a
data system) GC. When a data system, such as a
ChemStation or EZChrom Elite, controls the GC, methods
are stored in the data system and can be edited there. See
your data system documentation for more information.
Suppose your standalone GC is equipped with a single FID.
You have created and saved methods that use this detector.
Now you remove the FID and install a TCD in its place.
When you try to load one of your stored methods, you
observe an error message saying that the method and the
hardware do not match.
Advanced User Guide
81
6
Methods and Sequences
The problem is that the actual hardware is no longer the
same as the hardware configuration saved in the method.
The method cannot run because it does not know how to
operate the recently- added TCD.
On inspecting the method, you find that the detector- related
parameters have all been reset to the default values.
Correcting a method mismatch on a standalone GC
This problem can be avoided if you follow this procedure for
any hardware change, even including the simple replacement
of a defective detector board.
1 Before changing any hardware, press [Config][hardware
module], where [hardware module] is the device you intend
to replace.
82
2
Press [Mode/Type]. Select Remove module and press [Enter].
The module is now Unconfigured.
3
Turn the GC off.
4
Make the hardware change that you intended (in this
example, remove the FID and its flow module and replace
them with the TCD and its module).
5
Turn the GC on. Press [Config][hardware module].
6
Press [Mode/Type]. Select Install module and press [Enter].
The GC will install the new hardware module, which
corrects the active method (but not the stored one!).
7
Save the corrected method using the same number (which
overwrites the stored method) or a new number (which
saves both versions of the method).
Advanced User Guide
6
Methods and Sequences
Creating Sequences
A sequence specifies the samples to be run and the stored
method to be used for each. The sequence is divided into a
priority sequence (ALS only), subsequences (each of which
uses a single method), and post- sequence events
• Priority sequence—allows you to interrupt a running ALS
or valve sequence to analyze urgent samples. (See “About
the priority sequence” on page 83.)
• Subsequences—contain the stored method number and
information that defines a set of samples and calibrators
to be analyzed using a particular method. Sampler and/or
valve subsequences can be used in the same sequence.
• Post sequence—names a method to be loaded and run
after the last run in the last subsequence. Specifies
whether the sequence is to be repeated indefinitely or
halted after the last subsequence.
Samples in each subsequence are specified as either ALS
locations or sampling valve positions (gas sampling valves).
Five sequences with up to five subsequences each can be
stored.
About the priority sequence
The priority sequence consists of a single sampler or valve
subsequence and a special Use priority parameter, which can
be activated at any time, even when a sequence is running.
This feature allows you to interrupt a running sequence
without having to edit it.
If Use priority is On, then:
1 The GC and ALS complete the current run, then the
sequence pauses.
2
The GC runs the priority sequence.
3
The GC resets the Use priority parameter to Off.
4
The main sequence resumes where it paused.
To program a sequence
1 Press [Seq]. (Press again, if necessary, to display
subsequence information.)
2
Advanced User Guide
Create a priority sequence, if desired. (See “To program a
priority sequence” on page 84.) If you might want to use
83
6
Methods and Sequences
a priority sequence, you must program it now. (Once the
sequence starts, you cannot edit it without stopping it.)
3
Scroll to the Method # line of Subseq 1 and enter a method
number. Use 0 for the currently active method, 1 to 9 for
the stored methods, or [Off/No] to end the sequence.
4
Press [Mode/Type] to select a valve or injector type. (See
“To program a valve subsequence” on page 85 or “To
program an ALS subsequence” on page 85.)
5
Create the next subsequence or scroll to Post Sequence.
(See “To program post sequence events” on page 85.)
6
Save the completed sequence. (See “To save a sequence”
on page 86.)
To program a priority sequence
1 Press [Seq]. (Press again, if necessary, to display
subsequence information.)
2
Scroll to Priority Method # and enter a method number. Use
0 for the currently active method, 1 to 9 for the stored
methods, or [Off/No] to end the sequence. Press [Enter].
The active method, 0, will change during the sequence if
the subsequences use stored methods. Therefore,
method 0 should be chosen for the priority sequence only
if all subsequences use method 0.
3
Press [Mode/Type] and select the injector type.
4
Program the ALS subsequence. (See “To program an ALS
subsequence” on page 85.)
5
Store the completed sequence. (See “To save a sequence”
on page 86.)
Once a priority subsequence exists in a sequence, you can
activate it when the urgent samples are ready to be
processed by:
1 Press [Seq]. (Press again, if necessary, to display
subsequence information.)
2
Scroll to Use Priority and press [On/Yes].
When the priority samples are completed, the normal
sequence resumes.
84
Advanced User Guide
Methods and Sequences
6
To program an ALS subsequence
1 See step 1 through step 3 of “To program a sequence” on
page 83.
2
Press [Mode/Type] and select the injector type.
3
Enter injector sequence parameters:
• Number of Injections/vial—the number of repeat runs from
each vial. Enter 0 if no samples are to be injected.
• Samples—the range (first–last) of sample vials to be
analyzed.
4
Proceed with step 5 of “To program a sequence” on
page 83.
To program a valve subsequence
1 See step 1 through step 3 of “To program a sequence” on
page 83.
2
Press [Mode/Type] and select Valve.
3
Enter the valve sequence parameters :
• #inj/position—number of injections at each position
(0–99)
• Position rng—first–last valve positions to sample (1–32)
• Times thru range—number of times to repeat the range
(1–99)
• # injections—number of injections for each sample
4
Proceed with step 5 of “To program a sequence” on
page 83.
To program post sequence events
1 See step 1 through step 4 of “To program a sequence” on
page 83.
Advanced User Guide
2
Scroll to the Method # line of Post Sequence and enter a
method number. Use 1 to 9 for the stored methods, or 0 if
there is no method to be loaded.
3
Press [On/Yes] at Repeat sequence to keep repeating the
sequence (useful for valve sequences). Otherwise, press
[Off/No] to halt the sequence when all subsequences are
finished.
85
6
Methods and Sequences
To save a sequence
1 Press [Store][Seq].
2
Enter an identifying number for the sequence.
3
Press [On/Yes] to store the sequence. Alternatively, press
[Off/No] to cancel.
A message is displayed if a sequence with the number
you selected already exists.
• Press [On/Yes] to replace the existing sequence or
[Off/No] to cancel.
Sequences can also be stored from within the stored
sequence list ([Seq]) by scrolling to the appropriate sequence
number and pressing the [Store] key.
To load a stored sequence
Press [Load][Seq]. Supply the sequence number and press
[Enter]. The specified sequence will replace the current active
sequence.
To determine sequence status
Press [Seq Control] to display the current status of the active
sequence. There are six possible sequence status modes:
• Start/running
• Ready wait
• Paused/resume
• Stopped
• Aborted
• No sequence
To start a sequence
Press [Seq Control], scroll to Start sequence and press [Enter].
The sequence status will change to Running. The sequence
continues to run until all subsequences are executed, or
until one of the events described under “To abort a
sequence” on page 87 occurs.
86
Advanced User Guide
Methods and Sequences
6
Ready wait
If a sequence is started but the instrument is not ready (due
to oven temperature, equilibration times, etc.), the sequence
will not start until all instrument setpoints are ready
To pause and resume a sequence
Press [Seq Control], scroll to Pause sequence, and press [Enter].
The sequence status changes to paused, and you are given
the option to resume or stop the paused sequence.
The sequence halts when the current sample run is
complete.
To continue the paused sequence, scroll to Resume sequence
and press [Enter]. When a sequence is resumed, it starts with
the next sample.
To stop a sequence
A sequence automatically stops at the end of the last active
subsequence unless Repeat sequence is On in the Post
Sequence events.
To stop a running sequence, scroll to Stop sequence and press
[Enter]. A stopped sequence can only be restarted from the
beginning.
To abort a sequence
When a sequence is aborted, it stops immediately without
waiting for the current run to finish. These actions will
cause a sequence to abort:
• A run is stopped by pressing [Stop].
• A sampler error occurs producing an error message.
• The GC detects a configuration mismatch during a method
load.
• A running sequence tries to load an empty method.
• The sampler is turned off. You can correct the problem
and then resume the sequence. The aborted sample run
will be repeated.
Advanced User Guide
87
6
88
Methods and Sequences
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
7
Checking for Leaks
Preparing the GC for Maintenance 90
To Check for External Leaks 92
To Check for GC Leaks 93
To Perform a SS Inlet Pressure Decay Test 94
To Correct Leaks in the Split Splitless Inlet 98
To Perform a PP Inlet Pressure Decay Test 99
To Correct Leaks in the Packed Column Inlet 103
Agilent Technologies
89
7
Checking for Leaks
Preparing the GC for Maintenance
Before most maintenance procedures, the GC must be made
ready. The purpose of this preparation is to avoid damage to
both the instrument (electronics, columns, etc.) and the user
(shocks, burns).
Column and oven preparation
The main hazards here are temperature (burns) and column
exposure to air.
• Cool the oven by changing its setpoint to 35 °C. This
allows the oven fan to assist cooling.
• Leave the carrier gas flow On until the oven has cooled.
This protects the column from oxygen damage.
Inlet preparation
We are concerned with the possibility of burns and air
intrusion into the column.
• After the oven and columns have cooled, reduce all inlet
flows to 0.0 and turn the temperatures Off.
• For inlet- only maintenance, leave all detectors at their
normal setpoints except for the TCD filament, which
should be turned Off.
• If the column is to be removed, cap both ends to keep air
out.
Detector preparation
This is another burn hazard area, plus the possibility of
damage to the very sensitive electronics.
Some detectors (uECD, FPD, NPD) require 12 hours or
longer to stabilize from the detector- off condition.
• To cool the detector, reduce the temperature setpoint to
35 °C.
• Some detectors (FID, NPD, FPD) use high voltages. The
high voltage supply is part of the electrometer. Turn it Off
to disable the high voltage.
• The filament in the TCD will be damaged if exposed to
air while hot. To protect the filament, turn it Off.
90
Advanced User Guide
7
Checking for Leaks
Leak Check Tips
When checking for leaks, consider the system in two parts:
external leak points and GC leak points.
• External leak points include the gas cylinder (or gas
purifier), regulator and its fittings, supply shutoff valves,
and connections to the GC supply fittings.
• GC leak points include inlets, detectors, column
connections, valve connections, and connections between
flow modules and inlets/detectors.
WA R N I N G
Hydrogen (H2) is flammable and is an explosion hazard when
mixed with air in an enclosed space (for example, a flow meter).
Purge flowmeters with inert gas as needed. Always measure
gases individually. Always turn off detectors to prevent
flame/bead autoignition.
WA R N I N G
Hazardous sample gases may be present.
1 Gather the following:
• Electronic leak detector capable of detecting the gas
type
• 7/16, 9/16, and 1/4- inch wrenches for tightening
Swagelok and column fittings
2
Check any potential leak points associated with any
maintenance recently performed.
3
Check GC fittings and connections that undergo thermal
cycling, since thermal cycling tends to loosen some fitting
types. Use the electronic leak detector to determine if a
fitting is leaking.
• Start by checking any newly made connections.
• Remember to check connections in the gas supply lines
after changing traps or supply cylinders.
Advanced User Guide
91
7
Checking for Leaks
To Check for External Leaks
Check for leaks at these connections:
• Gas supply bulkhead fittings
• Gas cylinder fitting
• Regulator fittings
• Traps
• Shut- off valves
• T- fittings
Perform a pressure drop test.
1 Turn off the GC.
92
2
Set the regulator pressure to 415 kPa (60 psi).
3
Fully turn the regulator knob counterclockwise to shut
the valve.
4
Wait 5 minutes. If there is a measurable drop in pressure,
there is a leak in the external connections. No drop in
pressure indicates that the external connections are not
leaking.
Advanced User Guide
7
Checking for Leaks
To Check for GC Leaks
Check for leaks at these connections:
• Inlet septum, septum head, liner, split vent trap, split vent
trap line, and purge vent fittings
• Column connections to inlets, detectors, valves, splitters,
and unions
• Fittings from the flow modules to the inlets, detectors,
and valves
• Column adapters
• Agilent capillary flow fittings
Advanced User Guide
93
7
Checking for Leaks
To Perform a SS Inlet Pressure Decay Test
The pressure decay test checks for leaks from the inlet flow
module up to the column fitting.
After performing maintenance, first check for leaks in
externally accessible areas. See “To Check for External
Leaks”.
If a leak is known to exist, check the externally accessible
inlet fittings first, especially any connection that has seen
recent maintenance, such as the septum nut, column
adapter, column connection, and so forth.
The pressure decay leak test described below requires
removing the column and capping the inlet column fitting.
This test can/cannot find the following types of leaks:
The test can find leaks at the:
The test cannot find leaks at the:
septum
column fitting
septum nut
gas supply bulkhead fittings to the
flow module
liner O-ring seal
tubing and connections in a transfer
line connected to the inlet
gold seal/washer and reducing nut
internal leaks in an EPC module
inlet body
flow manifold split vent valve
split vent tubing and trap
septum purge tubing
seals within the tubing between the
inlet flow module and the inlet body
1 Gather the following (see Consumables and parts for the
split/splitless inlet):
• No- hole ferrule
• 1/4- inch wrench
• Heat- resistant gloves (if the inlet is hot)
• Column nut
• New septum
• O- ring
94
Advanced User Guide
7
Checking for Leaks
• ECD/TCD Detector plug (part no. 5060- 9055)
2
Load the inlet maintenance method and wait for the GC
to become ready.
3
Remove the column, if installed.
4
Plug the column fitting with a column nut and a no- hole
ferrule.
5
Remove the old septum and replace it with a new one.
See To change the septum on the split/splitless inlet.
6
Inspect the O- ring and replace it if it is hard and brittle
or cracked. See To change the liner and O- ring on the
split/splitless inlet.
7
Set the inlet to Split Mode.
8
Configure the column as Inlet: Unspecified.
9
Set the inlet temperature to 70 °C.
10 Enter a pressure setpoint of 25 psi (172 kPa). Make sure
that the pressure supplied to the GC is at least 10 psi
(70 kPa) higher than the inlet pressure.
11 If pressure cannot be achieved, there is either a large
leak or the supply pressure is too low.
12 Allow the inlet temperature to stabilize. Temperature
changes can invalidate the test.
13 Cap the septum purge fitting with the ECD/TCD detector
plug.
Advanced User Guide
95
7
Checking for Leaks
Back inlet split
vent
Back inlet purge
vent
Front inlet split
vent
Front inlet
purge vent
Front purge vent shown plugged
14 Press [Front or Back Inlet]. Scroll to Pressure and press
Off/No.
15 Quickly turn off the carrier gas supply at its source.
16 Monitor the pressure for 10 minutes. Use the timer by
pressing [Time] and [Enter].
A pressure drop of less than 0.5 psig (0.05 psi/min or
less; 3.4 kPa or 0.34 kPa/min) is acceptable.
96
Advanced User Guide
Checking for Leaks
7
If the pressure drops much faster than the acceptable
rate, see “To Correct Leaks in the Split Splitless Inlet”.
Retest.
Note that liner size impacts pressure drop. An inlet with
a smaller volume liner does not tolerate as large a leak
rate as an inlet with a larger volume liner.
17 After the inlet passes the test, restore the GC to
operating condition.
• Remove any caps/plugs.
• Reinstall the column.
• Restore the correct column configuration.
• Load the operating method.
Advanced User Guide
97
7
Checking for Leaks
To Correct Leaks in the Split Splitless Inlet
If the inlet fails a pressure decay test, check the following:
• Check the caps/plugs used in the test—make sure each is
correctly installed and tight.
• If you performed the leak test after performing
maintenance, check for proper installation of the part(s)
handled during the maintenance.
• Check the tightness of the septum nut. See To change the
septum on the split/Splitless inlet.
• Check the septum. Replace if old or damaged.
• Check the insert assembly installation.
• Check the liner and liner O- ring. See To change the liner
and O- ring on the split/splitless inlet.
• If you changed the gold seal, verify correct installation.
See To replace the gold seal on the split/splitless inlet.
• Make sure the inlet temperature remained constant during
the test.
If these items do not resolve the problem, contact Agilent for
service.
98
Advanced User Guide
7
Checking for Leaks
To Perform a PP Inlet Pressure Decay Test
The pressure decay test checks for leaks from the inlet flow
module up to the column fitting.
After performing maintenance, first check for leaks in
externally accessible areas. See “To Check for External
Leaks”.
If a leak is known to exist, check the externally accessible
inlet fittings first, especially any connection that has seen
recent maintenance, such as the septum nut, column
adapter, column connection, and so forth.
The pressure decay leak test described below requires
removing the column and capping the inlet column fitting.
This test can/cannot find the following types of leaks:
The test can find leaks at the:
The test cannot find leaks at the:
septum
column fitting
septum nut
gas supply bulkhead fittings to the
flow module
glass insert O-ring seal
adapter and ferrule
inlet body
top insert weldment
seals within the tubing between the
inlet flow module and the inlet body
WA R N I N G
This leak test is not appropriate for flammable carrier gases, such
as hydrogen.
1 Gather the following (see Consumables and parts for the
purged packed inlet):
• No- hole ferrule
• 1/4- inch wrench
• 7/16- inch wrench
• Heat- resistant gloves (if the inlet is hot)
• 9/16- inch wrench
Advanced User Guide
99
7
Checking for Leaks
• 1/8- and 1/4- inch Swagelok caps
• ECD/TCD Detector plug (part no. 5060- 9055)
2
Load the inlet maintenance method and wait for the GC
to become ready.
3
Remove the column, if installed.
4
Plug the column fitting.
• If the capillary column adapter is installed, use a
column nut and a no- hole ferrule
• If a 1/8- inch packed column adapter is installed, use a
1/8- inch Swagelok cap (5180- 4121).
• If a 1/4- inch packed column adapter is installed, use a
1/4- inch Swagelok cap (5180- 4120)
5
Remove the old septum and replace it with a new one.
See To change the septum on the purged packed inlet.
6
Inspect the O- ring and replace it if it is hard and brittle
or cracked. See To change the O- ring on the purged
packed inlet.
7
If unsure of the quality of the adapter ferrule, replace it.
See To change the glass insert on a PP inlet.
8
Set the inlet temperature to 150 °C.
9
Allow the inlet temperature to stabilize. Temperature
changes can invalidate the test.
10 Cap the septum purge fitting with the ECD/TCD detector
plug.
100
Advanced User Guide
7
Checking for Leaks
Back inlet split
vent
Back inlet purge
vent
Front inlet split
vent
Front inlet
purge vent
Front purge vent shown plugged
11 Monitor the inlet pressure. It should rise. When the
pressure rises above 25 psi (172 kPa), turn off the carrier
flow. (Press [Front Inlet] or [Back Inlet]. Scroll to Total flow
and press Off/No.)
If pressure cannot be achieved, there is either a large leak
or the supply pressure is too low.
12 Quickly turn off the carrier gas supply at its source.
13 Let the pressure stabilize for approximately 10 seconds.
The pressure should be between 25 and 28 psi (172 and
193 kPa).
14 Monitor the pressure for 5 minutes. Use the timer by
pressing [Time] and [Enter].
Advanced User Guide
101
7
Checking for Leaks
A pressure drop of less than 0.25 psig (0.05 psi/min or
less; 1.72 kPa or 0.34 kPa/min) is acceptable.
If the pressure drops much faster than the acceptable
rate, see “To Correct Leaks in the Packed Column Inlet”.
Retest.
15 After the inlet passes the test, restore the GC to
operating condition.
• Remove any caps/plugs.
• Reinstall the column.
• Restore the correct column configuration.
• Load the operating method.
102
Advanced User Guide
7
Checking for Leaks
To Correct Leaks in the Packed Column Inlet
If the inlet fails a pressure decay test, check the following:
• Check the caps/plugs used in the test—make sure each is
correctly installed and tight.
• If you performed the leak test after performing
maintenance, check for proper installation of the part(s)
handled during the maintenance.
• Check the tightness of the septum nut. See To change the
septum on the purged packed inlet.
• Check the septum. Replace if old or damaged.
• Check that the top insert weldment is installed tightly.
• Replace the O- ring. See To change the O- ring on the
purged packed inlet. Also check the glass insert. See To
change the glass insert on a PP inlet.
• Replace the ferrule seal on the adapter.
• Make sure the inlet temperature remained constant during
the test.
If these items do not resolve the problem, contact Agilent for
service.
Advanced User Guide
103
7
104
Checking for Leaks
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
8
Inlets
Using Hydrogen 106
Inlet Overview 107
Carrier Gas Flow Rates 108
About Gas Saver 109
Pre Run and Prep Run 110
Auto Prep Run 111
About Heaters 112
About the Split/Splitless Inlet 114
Split/Splitless inlet split mode overview 114
Split/Splitless inlet splitless mode overview 115
The S/SL inlet pulsed split and splitless modes 116
Split/Splitless inlet split mode minimum operating pressures 117
Selecting the correct S/SL inlet liner 118
Vapor Volume Calculator 120
Selecting parameters for the S/SL splitless mode 121
Agilent Technologies
105
8
Inlets
Using Hydrogen
106
WA R N I N G
When using hydrogen (H2), as the carrier gas, be aware that
hydrogen (H2) gas can flow into the oven and create an explosion
hazard. Therefore, be sure that the supply is off until all
connections are made, and ensure that the inlet and detector
column fittings are either connected to a column or capped at all
times when hydrogen (H2) gas is supplied to the instrument.
WA R N I N G
Hydrogen (H2) is flammable. Leaks, when confined in an enclosed
space, may create a fire or explosion hazard. In any application
using hydrogen (H2), leak test all connections, lines, and valves
before operating the instrument. Always turn off the hydrogen
(H2) supply at its source before working on the instrument.
Advanced User Guide
Inlets
8
Inlet Overview
Table 10
Comparing inlets
Inlet
Column
Mode
Sample
concentration
Split/splitless
Capillary
Split
Pulsed split
High
High
Splitless
Pulsed splitless
Low
Low
n/a
n/a
Any
Any
Packed column
Packed
Large capillary
Advanced User Guide
Comments
Useful with large
injections
Useful with large
injections
OK if resolution
not critical
Sample
to column
Very little
Very little
All
All
All
All
107
8
Inlets
Carrier Gas Flow Rates
The flow rates in Table 11 are recommended for all column
temperatures.
Table 11
Column type
Column size and carrier flow rate
Column size
Carrier flow rate, mL/min
Hydrogen
Packed
Capillary
108
Helium
Nitrogen
1/8-inch
30
20
1/4-inch
60
40
0.05 mm id
0.5
0.4
n/a
0.10 mm id
1.0
0.8
n/a
0.20 mm id
2.0
1.6
0.25
0.25 mm id
2.5
2.0
0.5
0.32 mm id
3.2
2.6
0.75
0.53 mm id
5.3
4.2
1.5
Advanced User Guide
8
Inlets
About Gas Saver
Gas saver reduces carrier flow from the split vent after the
sample is on the column. It applies to the Split/Splitless
inlet (all modes). It is most useful in split applications.
Column head pressure and flow rate are maintained, while
purge and split vent flows decrease. Flows—except column
flow—remain at the reduced level until you press [Prep Run].
[Start]
50
Split mode
Gas saver time, 3 min
Regular flow
[Prep Run]
Run ends
40
Split vent flow
mL/min
30
Gas saver flow
20 Gas saver flow
10
-2
-1
0
1
2
3
4
5
6
7
8
Time, min
[Start]
50
Splitless mode
Gas saver time, 5 min
Purge time, 2 min
[Prep Run]
40
Split vent flow
mL/min
Run ends
Purge flow
30
Gas saver flow
20 Gas saver flow
10
-2
-1
0
1
2
3
4
5
6
7
8
Time, min
To use gas saver
1 Press [Front Inlet] or [Back Inlet].
Advanced User Guide
2
Turn gas saver On.
3
Set Gas saver flow. It must be at least 15 mL/min greater
than the column flow.
4
If in split mode, set Saver time after injection time. In all
other modes, set after Purge time.
109
8
Inlets
Pre Run and Prep Run
With some inlets and operating modes, certain instrument
setpoints are different between runs than during an analysis.
To restore the setpoints for injection, you must place the GC
into the Pre Run state.
You must use the Pre Run state when:
• Using gas saver with any inlet.
• Using splitless mode with any inlet.
• Using a pressure pulse mode with any inlet.
There are three ways to begin Pre Run—manually (press
[Prep Run] before each run on the GC keypad or software
keypad), automatically (for Agilent samplers), or using Auto
Prep Run (for non- Agilent samplers). The three methods are
discussed below.
During the Pre Run state:
• The Run light blinks on the GC, and the Pre Run
indicator lights on the software keypad.
• Setpoints change to the correct values for injection.
• Inlet, detector, and oven equilibration times begin.
When all criteria for a run are met, the Not Ready light
turns off. The GC is now ready for sample injection.
The [Prep Run] key
Press [Prep Run] before you inject a sample manually. The GC
enters the Pre Run state. When the Run light stops blinking
and the Not Ready light goes off, begin the analysis.
Agilent samplers
If you are using an Agilent automatic sampling system, the
[Prep Run] function is automatic.
Start the sampler. It generates the [Prep Run] function, When
all the setpoints are reached and the GC becomes Ready,
sample injection begins.
110
Advanced User Guide
8
Inlets
Auto Prep Run
To set this parameter, usually for a non- Agilent integrator,
workstation, or other controlling device:
1 Press [Config] to view a list of configurable parameters.
Advanced User Guide
2
Scroll to Instrument and press [Enter].
3
Scroll to Auto prep run and press [On/Yes].
111
8
Inlets
About Heaters
Inlets (and detectors, valve boxes, etc.) are heated. There are
six heater connectors on the GC mainframe, located as
shown here:
Front of GC
Near top right corner
of front detector board
3
Near top right corner
of back detector board
4
End of valve bracket
5
1
2
Near front inlet
Near back inlet
All heater connectors are square, 4- conductor receptacles
mounted on brackets.
The next table describes the heater locations that are
available for each module.
Table 12
112
Heater connection locations by module
Module
Available heater connection location
Front inlet
1 or None
Back inlet
2 or None
Front detector
3
Back detector
4
PCM A
5 or 6 or 1 or 2
PCM B
5 or 6 or 1 or 2
PCM C
5 or 6 or 1 or 2
AUX 1,2,3
None
AUX 4,5,6
None
AUX 7,8,9
None
Valve box
5
Advanced User Guide
8
Inlets
Table 12
Heater connection locations by module (continued)
Module
Available heater connection location
Aux heater 1
5
Front FPD uses heater connectors 3 and 5.
Back FPD uses heater connectors 4 and 5.
Advanced User Guide
113
8
Inlets
About the Split/Splitless Inlet
This inlet is used for split, splitless, pulsed splitless, or
pulsed split analyses. You can choose the operating mode
from the inlet parameter list. The split mode is generally
used for major component analyses, while the splitless mode
is used for trace analyses. The pulsed splitless and pulsed
split modes are used for the same type of analyses as split
or splitless, but allow you to inject larger samples.
Septum tightening (S/SL)
Septum retainer nuts must be tightened enough to obtain a
good gas seal, but not so much as to compress the septum
and make it difficult to push a syringe needle through it.
For the standard septum retainer nut, an internal spring in
the septum retainer applies pressure to the septum. For inlet
pressures up to 100 psi, tighten the retainer until the C- ring
lifts about 1 mm above the top surface. This is adequate for
most situations.
1 mm
With higher inlet pressures, tighten the septum retainer until
the C- ring stops turning, indicating that the retainer is in
firm contact with the septum.
If using a Merlin Microseal™ septum, finger tighten the
septum nut, until snug (not loose). The pressure capacity
depends on the duckbill seal used.
Split/Splitless inlet split mode overview
During a split injection, a liquid sample is introduced into a
hot inlet where it vaporizes rapidly. A small amount of the
vapor enters the column while the major portion exits from
the split/purge vent. The ratio of column flow to split vent
flow is controlled by the user. Split injections are primarily
used for high concentration samples when you can afford to
lose most of the sample out the split/purge vent. It is also
used for samples that cannot be diluted.
114
Advanced User Guide
Inlets
8
The split ratio is equal to the split vent flow divided by the
column flow. If the column has been configured, the desired
split ratio can be entered directly.
The pneumatics for this inlet in split mode operation are
shown in the figure below.
Carrier Supply
80 PSI
Split
Septum Purge
EPC Module
Frit
Valve
Frit
Valve
FS
PS
Split Vent Trap
Inlet Weldment
FS = Flow Sensor
PS = Pressure Sensor
Column
Split/Splitless inlet splitless mode overview
In this mode, the split vent valve is closed during the
injection and remains so while the sample is vaporized in
the liner and transferred to the column. At a specified time
after injection, the valve opens to sweep any vapors
remaining in the liner out the split vent. This avoids solvent
tailing due to the large inlet volume and small column flow
rate. Specify the purge time and purge flow rate in the inlet
parameter list.
Advanced User Guide
115
8
Inlets
If you are using gas saver, the gas saver time should be after
the purge time.
Carrier Supply
80 PSI
Split
Septum Purge
EPC Module
Frit
Valve
Frit
Valve
FS
PS
Split Vent Trap
Inlet Weldment
FS = Flow Sensor
PS = Pressure Sensor
Column
The S/SL inlet pulsed split and splitless modes
The pressure pulse modes increase inlet pressure just before
the beginning of a run and return it to the normal value
after a specified amount of time. The pressure pulse:
• reduces the solvent vapor volume
• reduces the risk of inlet overload
• tightens the sample band
• may allow use of a 2 mm liner, reducing the active glass
area
If your chromatography is degraded by the pressure pulse, a
retention gap may help restore peak shape.
116
Advanced User Guide
8
Inlets
You must press [Prep Run] before doing manual injections in
the pressure pulse modes. See “Pre Run and Prep Run” on
page 110 for details.
You can do column pressure and flow programming when in
the pressure pulse mode. However, the pressure pulse will
take precedence over the column pressure or flow ramp.
Pressure pulse
Pressure
or
Flow
Pressure or flow program
0
1
2
3
4
5
6
7
8
Split/Splitless inlet split mode minimum operating pressures
The minimum recommended inlet total flow is
20 mL/minute. When the split/splitless inlet is operated in
Split mode, there will be a minimum pressure at which the
inlet can operate. Typically, low inlet pressures may be
required for shorter, wide bore columns. The minimum
pressure is a function of carrier gas type, total inlet flow,
liner design, and possible contamination of the split vent
tube or trap.
A wide bore column requires a much lower inlet pressure
than a typical capillary column to maintain a given flow.
Setting the split ratio (total flow) too high when using a
wide bore column can create an unstable control
relationship between the pressure and flow control loops.
Advanced User Guide
117
8
Inlets
Table 13
Approximate minimum viable inlet pressures for split/splitless inlet in split mode, in psi (kPa)
Split vent flow (mL/min)
50–100
100–200
200–400
400–600
Split liners - 5183-4647, 19251-60540
2.5 (17.2)
3.5 (24.1
4.5 (31)
6.0 (41.4)
Splitless liners - 5062-3587, 5181-8818
4.0 (27.6)
5.5 (37.9)
8.0 (55.2)
11.0 (75.4)
Split liners - 19251-60540, 5183-4647
3.0 (20.7)
4.0(27.6)
—
—
Splitless liners - 5062-3587, 5181-8818
4.0 (27.6)
6.0 (41.4)
—
—
Helium and hydrogen carrier gases
Nitrogen carrier gas
These numbers are based on the resistance to flow of new,
clean inlet systems. Sample condensation in the split vent
tube or a dirty filter can make these values non- attainable.
Selecting the correct S/SL inlet liner
Split liner
A good liner for split mode operation will offer very little
restriction to the split flow path between the bottom of the
liner and the inlet gold seal and between the outside of the
liner and the inside of the injection port body. The preferred
Agilent split liner, part number 5183- 4647, incorporates a
glass positioning bead on the bottom to facilitate this. It will
also incorporate glass wool or some other source of surface
area inside the liner that provides for complete sample
vaporization across the boiling point range of the sample.
Select an appropriate liner from Table 14.
Table 14
Liner
118
Split mode liners
Description
Volume
Mode
Deactivated
Part Number
Low Pressure Drop
– Positioning Bead
870 µL
Split – Fast
Injection
Yes
5183-4647
4mm ID, Glass Wool 990 µL
Split – Fast
Injection
No
19251-60540
Empty Pin & Cup
800 µL
Split – Manual
Only
No
18740-80190
Packed Pin & Cup
800 µL
Split – Manual
Only
No
18740-60840
Advanced User Guide
8
Inlets
Splitless liner
The liner volume must contain the solvent vapor. The liner
should be deactivated to minimize sample breakdown during
the purge delay. Solvent vapor volume can be reduced by
using Pulsed Splitless mode. Use the “Vapor Volume
Calculator“ to determine vapor volume requirements.
Vapor volume < 300 µL Use 2 mm liner (250 µL volume),
5181- 8818 or similar.
Vapor volume 225 – 300 µL
reduce vapor volume.
Vapor volume > 300 µL
Consider pulsed splitless mode to
Use 4 mm liner, 5062- 3587 or similar.
Vapor volume > 800 µL Consider pulsed splitless mode to
reduce vapor volume.
For thermally labile or reactive samples, use G1544- 80700
(open top) or G1544- 80730 (top taper) liners.
Table 15
Splitless mode liners
Liner
Advanced User Guide
Description
Volume
Mode
Deactivated Part Number
Single Taper Glass
Wool
900 uL
Splitless
Yes
5062-3587
Single Taper
900 uL
Splitless
Yes
5181-3316
Dual Taper
800 uL
Splitless
Yes
5181-3315
2 mm Quartz
250 uL
Splitless
No
18740-80220
2 mm Quartz
250 uL
Splitless
Yes
5181-8818
1.5 mm
140 uL
Direct
No
Inject, Purge
and Trap,
Headspace
18740-80200
Single Taper Glass
Wool
900 uL
Splitless
Yes
5062-3587
Single Taper
900 uL
Splitless
Yes
5181-3316
4 mm Single Taper
Direct column connect
Yes
G1544-80730
4 mm Dual Taper
Direct column connect
Yes
G1544-80700
119
8
Inlets
Vapor Volume Calculator
Agilent provides a Vapor Volume Calculator to help you
determine if a liner is suitable for a method. To use the
calculator install the Agilent Instrument utility provided with
the GC. The calculator is also provided with the Agilent
Instrument Utilities software.
Setting parameters for the S/SL split mode
Mode
The current operating mode—split
Temperature
Pressure
Actual and setpoint inlet temperatures
Actual and setpoint inlet pressure
Split ratio The ratio of split vent flow to column flow.
Column flow is set at the Column parameter list. This line
appears only if your columns in the flow path are defined.
Split flow Flow, in mL/min, from the split vent. This line
appears only if your columns in the flow path are defined.
Total flow This is the total flow into the inlet, which is the
sum of the split vent flow, column flow, and septum purge flow.
When you change the total flow, the split ratio and split vent flow
change while the column flow and pressure remain the same.
If all columns in the flow path are defined
1 Press [Front Inlet] or [Back Inlet].
2
Scroll to Mode: and press [Mode/Type]. Select Split.
3
Set the inlet temperature.
4
If you want a specific split ratio, scroll to Split ratio and
enter that number. Split flow will be calculated for you.
5
If you want a specific split flow, scroll to Split flow and
enter that number. Split ratio will be calculated for you.
6
If desired, turn on Gas saver. Set Saver time after the
injection time. Press [Prep Run] (see “Pre Run and Prep
Run” on page 110) before manually injecting the sample.
If a column in the flow path is not defined
1 Press [Front Inlet] or [Back Inlet].
2
120
Set the inlet temperature.
Advanced User Guide
8
Inlets
3
Set Total flow into the inlet. Measure the split vent flow
using a flow meter.
4
Subtract split vent flow and septum purge flow (see “Pre
Run and Prep Run” on page 110) from Total flow to get
column flow.
5
Calculate the split ratio (split vent flow/column flow).
Adjust as needed.
Selecting parameters for the S/SL splitless mode
A successful splitless injection consists of these steps:
1 Vaporize the sample and solvent in a heated inlet.
2
Use a low flow and low oven temperature to create a
solvent- saturated zone at the head of the column.
3
Use this zone to trap and reconcentrate the sample at the
head of the column.
4
Wait until all, or at least most, of the sample has
transferred to the column. Then discard the remaining
vapor in the inlet—which is mostly solvent—by opening a
purge valve. This eliminates the long solvent tail that this
vapor would otherwise cause.
5
Raise the oven temperature to release the solvent and
then the sample from the head of the column.
Some experimentation is needed to refine the operating
conditions. Table 16 provides starting values for the critical
parameters.
Table 16
Advanced User Guide
Splitless mode inlet parameters
Parameter
Allowed setpoint range
Suggested starting
value
Oven temperature
24 °C to 425 °C
10 °C below solvent
boiling point
Oven initial time
0 to 999.9 minutes
≥ Inlet purge time
Inlet purge time
0 to 999.9 minutes
2 x Liner volume
Column flow
Gas saver time
0 to 999.9 minutes
After purge time
Gas saver flow
15 to 1000 mL/min
15 mL/min greater than
maximum column flow
121
8
Inlets
Setting parameters for the S/SL splitless mode
Mode
The current operating mode—splitless
Oven temperature
Temperature
Pressure
kPa
Below solvent boiling point
Actual and setpoint inlet temperatures
Actual and setpoint inlet pressure in psi, bar, or
Purge time The time, after the beginning of the run, when
you want the purge valve to open. This is the time in which
the vaporized sample transfers from the liner to the column.
Purge flow The flow, in mL/min, from the purge vent, at
Purge time. You will not be able to specify this value if any
column in the flow path is not defined.
Total flow
The actual flow to the inlet during a Pre- run
(Pre- run light is on and not blinking) and during a run
before purge time. You cannot enter a setpoint at these
times. At all other times, Total flow will have both setpoint
and actual values.
If all columns in the flow path are defined
1 Press [Front Inlet] or [Back Inlet].
2
Scroll to Mode: and press [Mode/Type]. Select Splitless.
3
Set the inlet temperature.
4
Enter a Purge time and a Purge flow.
5
If desired, turn on Gas saver. Make certain the time is set
after the Purge time.
6
Press [Prep Run] (see “Pre Run and Prep Run” on
page 110) before manually injecting a sample (this is
automatic for Agilent ALS).
If a column in the flow path is not defined
1 Press [Front Inlet] or [Back Inlet].
122
2
Scroll to Mode: and press [Mode/Type]. Select Splitless.
3
Set the inlet temperature.
4
Enter a Purge time.
Advanced User Guide
8
Inlets
5
Set your Total flow greater than the sum of column flow
plus the septum purge flow—see “Pre Run and Prep Run”
on page 110—to guarantee adequate column flow.
6
Press [Prep Run] (see “Pre Run and Prep Run” on
page 110) before manually injecting a sample.
Setting parameters for the S/SL pulsed modes
The pulsed mode parameters are the same as the non- pulsed
parameters, but with two additional values.
Pulsed pressure The inlet pressure you want at the start of
the run. The pressure rises to this value when [Prep Run] is
pressed and remains constant until Pulse time elapses, when
it returns to Pressure.
Pulse time This is the time after the start of the run when
the inlet pressure returns to Pressure.
“Pre Run and Prep Run” on page 110“Pre Run and Prep
Run” on page 110“Pre Run and Prep Run” on page 110“Pre
Run and Prep Run” on page 110The preferred technique for
concentrating analytes in the inlet liner is to use a single,
large volume injection. Using a high capacity syringe and one
septum puncture reduces the possibility of contamination
and generally improves results when compared against a
multiple septum puncture technique. However, if needed, you
can perform multiple septum punctures during the vent
time. This technique requires an Agilent data system and
automatic liquid sampler.
. The configured syringe size changes the available choices
for injection volume.
Injection volume — Select the injection volume, then enter a
number of injections. The total injection volume will be
displayed.
Preinjection washes and pumps are performed only before
the first injection of a multiple injection set.
Advanced User Guide
123
8
Inlets
About the Packed Column Inlet
This inlet is also known as the purged packed inlet (PP). It
is used with packed columns when high- efficiency
separations are not required. It can also be used with
wide- bore capillary columns, if flows greater than
10 mL/min are acceptable.
The inlet is flow controlled, regardless or whether or not the
column is capillary and defined, or packed.
Carrier Supply
80 PSI
Septum Purge
EPC Module
Frit
Frit
Valve
FS
PS
Inlet Weldment
FS = Flow Sensor
PS = Pressure Sensor
Column
Setting parameters
The inlet operates in flow control mode.
124
Advanced User Guide
8
Inlets
While in flow control mode, you cannot enter pressures here.
Temperature
The setpoint and actual temperature values.
Pressure The actual pressure (in psi, bar, or kPa) supplied
to the inlet. You cannot enter a setpoint here.
Total flow Enter your setpoint here, actual value is
displayed. Inlet is mass flow controlled.
Advanced User Guide
125
8
126
Inlets
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
9
Columns and Oven
About the Oven 128
Oven safety 128
Configuring the Oven 129
About Oven Temperature Programming 130
Programming setpoints 130
Oven ramp rates 131
Setting the oven parameters for constant temperature 131
Setting the oven parameters for ramped temperature 132
About Columns 133
Nickel Catalyst Tube 137
About the nickel catalyst tube 137
Nickel catalyst gas flows 137
Setting temperatures for the nickel catalyst tube 138
Agilent Technologies
127
9
Columns and Oven
About the Oven
Table 17
Oven capabilities
Capability
Range
Temperature range
0 °C to the configured limit
Maximum temperature
425 °C
(100 V oven: 350°C)
Temperature programming
Up to five ramps
Maximum run time
999.99 minutes
Temperature ramp rates
0 to 75 °C/min, depending on
instrument configuration
(100 V oven: 0 to 30 °C/min)
Oven safety
For safety, opening the oven door turns off power to the
oven heater, and fan, but maintains the setpoints in memory.
Closing the oven door returns the oven to normal operation.
If the oven cannot attain or maintain an entered setpoint
temperature during normal above- ambient operation, a
problem is assumed and the oven is switched off.
Possible problems include:
• The oven vent flaps not working
• The oven fan, heater, or temperature sensor not working
properly
• An electronic problem
When a shutdown occurs, the Off line in the oven parameter
list blinks and the oven remains off until switched on again
by pressing [Oven][On] or by editing the Temperature setpoint.
128
Advanced User Guide
Columns and Oven
9
Configuring the Oven
Oven configuration sets maximum temperature, equilibration
time, and the cool down mode.
Maximum temperature Maximum allowable oven temperature
setpoint. Some accessories, such as the valve box, valves and
columns have specific temperature limits. When configuring
Maximum temperature, these limits should be considered so
that the accessories are not damaged. Oven setpoints are
verified as they are entered; a message is displayed when an
entered setpoint is inconsistent with a previously defined
maximum.
Equilibration time The time required for the oven
temperature to equilibrate after temperature is modified.
Equilibration time begins when the actual oven temperature
comes within 1 °C of the oven temperature setting. The
Equilibration time setpoint can be 0 to 999.99 minutes.
Advanced User Guide
129
9
Columns and Oven
About Oven Temperature Programming
You can program the oven temperature from an initial
temperature to a final temperature using up to 5 ramps
during a run.
A single ramp temperature program raises the initial oven
temperature to a specified final temperature at a specified
rate and holds at the final temperature for a specified
period of time.
Final temperature 1
Final time 1
Rate 1
Rate 2 = 0
Initial time 1
Initial temperature
The multiple- ramp temperature program is similar. You can
program the oven from an initial temperature to a final
temperature, but with various rates, times, and temperatures
in between. Multiple ramps can also be programmed for
temperature decreases as well as increases.
Final temperature 2
Final time 2
Rate 2
Final temperature 1
Initial temperature
Final time 1
Rate 3 = 0
Rate 1
Initial time 1
Programming setpoints
Temperature Starting temperature of a temperature
programmed run. When the program begins, this value is
copied into a temporary setpoint called Init temp. At the end
of the run, Temperature is reset to the value in Init temp and
the oven returns to its starting temperature.
Initial time Time in minutes that the oven will stay at the
starting temperature after a programmed run has begun.
Rate The rate in °C/min at which the oven will be heated
or cooled.
130
Advanced User Guide
9
Columns and Oven
Final temperature Temperature of the oven at the end of a
heating or cooling rate.
Final time Time in minutes that the oven will be held at the
final temperature of a temperature- programmed rate.
Total length of a run is determined by its oven temperature
program. The maximum allowable time for a run is
999.99 minutes. If the program is still running at that time,
the run terminates.
See also “Post Run Programming.”
Oven ramp rates
The highest rate that you can achieve depends on many
factors, including the room temperature, temperatures of the
inlets and detectors, the amount of material inside the oven
(columns, valves, etc.), and whether or not this is the first
run of the day.
Table 18 lists typical oven ramp rates.
Table 18
Oven ramp rates
Temperature range (°C)
100 V oven
ramp rate (°C/minute)
200/220/230/240 V
oven
ramp rate (°C/minute)
50 to 70
30
75
70 to 115
30
45
115 to 175
30
40
175 to 300
30
30
300 to 425
20
20
Setting the oven parameters for constant temperature
An isothermal run is one in which the oven is maintained at
a constant temperature. For an isothermal run, set Rate 1 to
zero.
1 Press [Oven] to open the oven parameter list.
Advanced User Guide
2
Enter the oven temperature for the isothermal run.
3
Enter the number of minutes (Initial time) that you want
the oven to stay at this temperature. This time is the
duration of the run.
131
9
Columns and Oven
4
If Rate 1 is not already 0, enter zero for an isothermal
run.
Setting the oven parameters for ramped temperature
Single ramp
1 Press [Oven] to open the oven parameter list.
2
Enter a starting temperature (Temperature).
3
Enter the time (Initial time) that you want the oven to stay
at Temperature.
4
Enter the rate (Rate 1) at which the oven temperature is
to change.
5
Enter the final temperature (Final temperature 1).
6
Enter the time (Final time 1) the oven is to hold Final
temperature 1.
7
To end the oven ramp program after Ramp 1, set Rate 2 to
zero.
Multiple ramps
In a multiple- ramp program, Final time for one ramp is also
Initial time for the next ramp. Thus, there is only one Initial
time.
1 Set up the first oven ramp as described in “Single ramp”.
132
2
Enter the rate (Rate 2) at which you want the oven
temperature to increase for the second oven ramp.
3
Enter the final temperature (Final temperature 2).
4
Enter the number of minutes (Final time 2) that you want
the oven to hold the final temperature.
5
To end the temperature program after the second ramp,
set Rate 3 to zero.
6
To add additional oven ramps, repeat the steps described.
Advanced User Guide
9
Columns and Oven
About Columns
In all GCs, a sample—which is a mixture of several
components—is vaporized in an inlet, separated in a column,
and examined in a detector.
The column separates components in time because:
• When a vaporized component is presented with a gas
phase and a coating phase, it divides between the two
phases according to its relative attraction to the two
phases.
• The “attraction” can be solubility, volatility, polarity,
specific chemical interaction, or any other property that
differs from one component to another.
• If one phase is stationary (the coating) and the other is
moving (the carrier gas), the component will travel at a
speed less than that of the moving phase. How much less
depends on the strength of the attraction.
• If different components have different “attractions”, they
will separate in time.
Selecting the correct packed glass column type
This topic is covered in the Maintenance manual. See To
attach a packed column to the purged packed inlet for
details.
About the column modes
The flow modes available are determined by the GC inlet’s
control mode. When the inlet’s control mode is set to
Pressure control, all of the flow modes and pressure modes
below are available for the column. When the inlets control
mode is set to Flow control, the column’s mode is not
selectable. For an inlet’s mode of Flow control, only column
flow can be entered.
The flow modes
Flow rates are corrected to NTP (normal temperature and
pressure, 25 °C and 1 atmosphere.
Advanced User Guide
133
9
Columns and Oven
• Constant flow—Maintains a constant mass flow rate of
carrier gas in the column throughout the run. If the
column resistance changes due to a temperature program,
the column head pressure is adjusted to keep the flow
rate constant. This can shorten runs significantly.
• Ramped flow—Increases the mass flow rate in the column
during the run according to a program you enter. A
column flow profile can have up to three ramps, each
consisting of a programmed increase followed by a hold
period.
The pressure modes
The pressure modes are not available if the column is not
defined or the inlet’s mode is set to Flow control.
Pressures are gauge pressures—the difference between the
absolute pressure and the local atmospheric pressure.
Because most detectors present little resistance to the
column flow, the gauge pressure at the column head is
usually the same as the pressure difference between column
inlet and exit. The mass selective detector and the atomic
emission detector are the exceptions.
• Constant pressure—Maintains a constant gauge pressure
at the head of the column throughout the run. If the
column resistance and gas density changes during a run,
the gauge pressure does not change but the mass flow
rate does.
• Ramped pressure—Increases the column head gauge
pressure during the run according to a program you
enter. A column pressure profile can have up to three
ramps, each consisting of a programmed increase followed
by a hold period.
Select a column mode
The column’s mode parameter is not available if the inlet’s
mode parameter is set to Flow control.
1 Press [Col #] and enter the column number.
134
2
Scroll to the Mode line.
3
Press [Mode/Type] to see the column mode list.
4
Scroll to the column mode you want. Press [Enter].
Advanced User Guide
9
Columns and Oven
This completes column mode selection. Next you must
specify the inlet conditions either during the entire run (if
you selected either of the constant modes) or at the
beginning of the run (if you selected either of the ramped
modes).
Setting the column parameters for constant flow or constant pressure
If the column is defined, you can enter any one of these
quantities—the GC will calculate and display the other two.
For example, you may have selected Constant pressure as the
column mode. You decide to specify, as a starting condition,
the column flow. The GC will compute the pressure
necessary to achieve this flow (as well as the average linear
velocity) and hold this pressure constant during the run.
If you select Constant flow as the mode and specify column
flow as the initial condition, the GC will still calculate the
pressure necessary to achieve this flow, but it will adjust the
pressure as necessary to maintain constant flow.
If the column is not defined, you can enter only pressure.
Constant flow can still be specified, but the GC cannot know
what the flow is.
1 Press [Col #] and enter the column number.
2
Scroll to the Pressure or Flow or Velocity line.
3
Type the desired initial value, followed by [Enter]. The GC
will compute and display the other two values. Adjust
them, if you choose to, by repeating steps 2 and 3 but
note that changing any one changes all three.
This completes setting the initial carrier gas condition.
Enter a flow or pressure program (optional)
If you selected either the ramped pressure or ramped flow
column mode, the column parameter list contains entries for
setting up a ramp program.
You begin with an initial value, either Initial Pressure or Initial
Flow, and an Initial time. At the end of that time, Rate 1 begins
and runs until it reaches Final pressure (or Final flow). It
remains at that value for Final time 1. You can then add a
second and third ramp, each consisting of a Rate, a Final
value (pressure or flow), and a Final time.
The program ends when it reaches a Rate that is set to 0
(Off).
Advanced User Guide
135
9
Columns and Oven
When a flow or pressure program is running, the Pressure,
Flow, and Velocity lines that you used to set constant
conditions show the progress of the program.
The oven program determines the length of the run. If a
flow or pressure program ends before the analytical run
does, the flow (or pressure) remains at the last final value.
Programming column pressure or flow
1 Press [Col #] then enter the column number.
136
2
Scroll to Initial pressure (or Initial flow). Type the desired
value and press [Enter].
3
Similarly, enter a value for Initial time. This completes the
initial part of the program.
4
To begin a ramp, enter a positive value for Rate 1. It does
not matter whether you are programming up or
down—the rate is always positive.
5
If Rate 1 is zero, the program ends here. If you enter any
other value, the Final value lines for the first ramp
appear and the cursor moves to the line.
6
Enter values for Final pressure 1 (or Final flow 1) and Final
time 1. This completes the first ramp.
7
To enter a second ramp, scroll to the appropriate Rate
line and repeat steps 5 and 6. A maximum of 3 ramps
can be entered.
Advanced User Guide
9
Columns and Oven
Nickel Catalyst Tube
About the nickel catalyst tube
The Nickel Catalyst Tube accessory, G4337A, is used for
trace analysis of CO and CO2 with a flame ionization
detector. The gas sample is separated on the column and
passed over a heated catalyst in the presence of hydrogen,
which converts the CO and CO2 peaks to CH4.
Sample
Carrier gas
Hydrogen
Column
Gas sample valve
Air
Nickel catalyst
FID
Nickel catalyst gas flows
For a standard FID installation:
Table 19
Advanced User Guide
Gas flows for a standard FID
Gas
Flow rate, mL/min
Carrier (helium)
30
FID hydrogen
30 (see Caution)
FID air
400
137
9
Columns and Oven
Table 20
CAUTION
Gas flows for a TCD/FID series installation
Gas
Flow rate, mL/min
Carrier (helium)
30
TCD switching flow
25
FID hydrogen
45 (see Caution)
FID air
500
Hydrogen flow is pressure-controlled, where an FID provides a
known resistance. The nickel catalyst tube increases flow
resistance, so that the calibration is no longer valid. You must
measure hydrogen flow with a bubble or similar meter.
The nickel catalyst can be damaged by exposure to air.
Setting temperatures for the nickel catalyst tube
The nickel catalyst tube is usually mounted in the back inlet
position and controlled by the back inlet temperature
setpoint. For most analyses, set these temperatures:
• Nickel catalyst tube—375 °C
• FID—400 °C
138
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
10
Detectors
About Makeup Gas 140
About the FID 141
About the TCD 146
About the uECD 154
About the NPD 160
About the FPD 171
Agilent Technologies
139
10 Detectors
About Makeup Gas
Most detectors use a makeup gas to increase the flow rate
through the detector body. This sweeps peaks out of the
detector quickly, avoiding mixing of components and loss of
resolution. This is particularly important with capillary
columns because the column flow rates are so small.
The makeup gas line of your detector parameter list changes
depending on your instrument configuration.
If you have an inlet with the column not defined, the
makeup flow is constant. If you are operating with column
defined, you have a choice of two makeup gas modes.
Constant makeup This mode provides a constant flow of
makeup gas to the detector.
Column + makeup = constant This mode provides a variable
flow of makeup gas to the detector. As column flow
increases or decreases, the makeup flow changes to provide
a constant combined flow to the detector. If you choose this
option, enter a value under Combined flow. The Combined flow
line always displays the same value, while the Makeup line
changes as the actual makeup flow changes.
To change the makeup gas flow mode
1 Press [Front Det] or [Back Det].
140
2
Scroll to Mode. Press [Mode/Type].
3
Scroll to the correct mode and press [Enter].
Advanced User Guide
Detectors
10
About the FID
The FID passes sample and carrier gas from the column
through a hydrogen- air flame. The hydrogen- air flame alone
creates few ions, but burning an organic compound increases
the number of ions produced. A polarizing voltage attracts
these ions to a collector located near the flame. The current
produced is proportional to the amount of sample being
burned. This current is sensed by an electrometer, converted
to digital form, and sent to an output device.
The FID uses three supply gases (hydrogen, makeup gas, and
air) and two supply lines. Air flows through one supply line,
while hydrogen mixed with the makeup gas flows through
the other. All three supply gases use:
• A filter frit to protect the flow path and limit the flow
rate
• A proportional valve to control the pressure
• A pressure sensor and restrictor to control the valve
The hydrogen and makeup mix outside the flow module and
enter the detector at the base of the jet. Air enters above
the jet.
Advanced User Guide
141
10 Detectors
H2
Makeup
Air
EPC Module
Frit
Frit
Frit
Valve
Valve
Valve
PS
PS
Frit
Frit
PS
Frit
PS = Pressure Sensor
Column
How FID units are displayed in Agilent data systems and on the GC
The GC displays the FID signal in picoamperes (pA). The
following table lists how different data systems convert the
display units to reporting units.
Table 21
Unit conversions
Data system
Height units
LSV (height units)
Area units
Noise (ASTM)*
Agilent data system
1 pA
1.3 x10-4 pA
1 pA-sec
0.038 pA
SIGRange† 0
1 x 10-4 pA
1.3 x 10-4 pA
1 x 10-4 pA
0.038 pA
SIGRange 5
3.2 x 10-3 pA
4.2 x 10-3 pA
3.2 x 10-3 pA
0.038 pA
Analog 1V
‡
-4
1.25 x 10 pA
device dependent
-4
1.25 x 10 pA
0.038 pA
* Noise is recommended maximum when determining MDL.
† SIGRange used with 3393 and 3396 integrators.
‡ Analog 1V is an approximate value.
142
Advanced User Guide
Detectors
10
To light the FID flame
Press [Front Det] or [Back Det], scroll to Flame, then press
[On/Yes].
To extinguish the FID flame
Press [Front Det] or [Back Det], scroll to Flame, then press
[Off/No].
FID automatic reignition (Lit offset)
Lit offset is the expected minimum difference between the FID
output with the flame lit and the output with the flame off.
The GC checks this value during runs and when loading a
method.
During a run, if the output falls below the Lit offset value, the
FID will attempt to reignite three times. If after the third
attempt the output does not increase by at least this value,
the detector shuts down all functions except temperature
and makeup gas flow.
When loading a method that includes a Flame On setting, the
GC performs a similar check. If the detector output is less
than the Lit offset, it will attempt reignition after reaching
method setpoints.
The default setting for Lit offset is 2.0 picoamps. This is a
good working value for all but very clean gases and systems.
You may want to lower this setpoint if the detector attempts
to reignite when the flame is still on, thus producing a
shutdown.
To change Lit offset:
1 Press [Config][Front Det] or [Config][Back Det].
2
Scroll to Lit offset.
3
Enter the new value and press [Enter].
Recommended starting conditions for new FID methods
See Table 22 for guidelines and rules to select initial
detector settings for new methods.
Advanced User Guide
143
10 Detectors
Table 22
Recommended starting conditions
Combustible gas mix
Make sure that the final hydrogen-to-air ratio is between 8% and 12%
Detector temperature
Set to 20 °C above the highest oven temperature, depending on the column type.
A temperature of 300 °C provides a good starting point and easier ignition, and
minimizes water condensation.
The GC will not attempt to ignite the flame at a temperature <150 °C.
Carrier gas flow (hydrogen, helium,
nitrogen)
Packed columns
Suggest 10 to 60 mL/min
Capillary columns
Suggest 1 to 5 mL/min
Detector gases
Flow range mL/min
Suggested flow mL/min
Column plus capillary makeup
10 to 60
30
Hydrogen
24 to 60
30
Air
200 to 600
400
Column plus capillary makeup
10 to 60
30
Hydrogen
24 to 60
30*
Air
200 to 600
400
Standard installation
With Nickel Catalyst Accessory:
Standard installation
* Detector hydrogen is pressure controlled, where the detector provides a known resistance. If using a nickel catalyst tube, the resistance
changes, and the flow rates displayed by the GC will not be accurate. Measure the actual hydrogen flow using a flow meter at the detector
vent, with all other flows turned off.
Use nitrogen makeup gas (instead of helium) for greater
sensitivity.
Setting parameters for FID
WA R N I N G
144
Verify that a column is installed or the FID column fitting is
plugged before turning on the air or hydrogen. An explosion may
occur if air and hydrogen are allowed to leak into the oven.
Advanced User Guide
10
Detectors
To set the FID parameters:
1 Verify:
• Makeup gas is configured
• Installed jet type is correct for column type
2
Press [Front Det] or [Back Det].
3
Set the detector temperature. The temperature must be
greater than 150 °C for the flame to light.
4
Set the hydrogen flow rate, if desired, and press [Off/No].
5
Change the air flow rate, if desired, and press [Off/No].
6
If using a packed column, set the FID makeup gas to
0.0/Off.
7
If using a defined capillary column, set the makeup gas
flow or combined column plus makeup gas flow.
8
Scroll to Flame and press [On/Yes]. This turns on the air
and hydrogen and initiates the ignition sequence. The
signal typically increases to 5 to 20 pA after ignition.
Verify that the flame is lit by holding a cold, shiny
surface, such as a mirror or chrome- plated wrench, over
the collector exit. Steady condensation indicates that the
flame is lit.
Advanced User Guide
145
10 Detectors
About the TCD
The TCD compares the thermal conductivities of two gas
flows—pure carrier gas (the reference gas) and carrier gas
plus sample components (the column effluent).
This detector contains a filament that is heated electrically
so that it is hotter than the detector body. The filament
temperature is held constant while alternate streams of
reference gas and column effluent pass over it. When a
sample component appears in the effluent, the power
required to keep the filament temperature constant changes.
The two gas streams are switched over the filament five
times per second (hence the ticking sound) and the power
differences are measured and recorded.
When helium (or hydrogen) is used as carrier gas, the
sample causes the thermal conductivity to fall. If nitrogen is
used, the thermal conductivity usually goes up because most
things are more conductive than nitrogen.
Because the TCD does not destroy the sample during the
detection process, this detector can be connected in series to
a flame ionization detector or other detector.
146
Advanced User Guide
Detectors
Column effluent
is forced away from
the filament. TCD
measures reference gas.
Advanced User Guide
10
Column effluent
is forced toward
the filament. TCD
measures peaks
(if present).
147
10 Detectors
TCD pneumatics
This is the pneumatics design of the TCD.
Makeup
Reference gas
EPC Module
Frit
Frit
Frit
Valve
Valve
Valve
Vent
PS
PS
Frit
PS
Frit
Reference
switching valve
PS = Pressure Sensor
Column
TCD carrier, reference, and makeup gas
Reference and makeup gas must be the same as the carrier
gas, and the gas type must be specified in both the inlet and
detector parameter lists.
When using packed columns, we recommend a small makeup
gas flow (2 to 3 mL/min) to get the best peak shapes.
Use the next figure to select a value for reference gas flow
for either capillary or packed columns. Any ratio within
±0.25 of that in the figure is suitable.
148
Advanced User Guide
10
Detectors
4.0
3.0
Ratio of reference flow to
column + makeup flow
2.0
1.0
0
10
20
30
40
50
60
Column + makeup flow, mL/min
TCD gas pressures
Choose a flow, find a pressure, set source pressure 10 psi
(70 kPa) higher.
4
Hydrogen
Helium
3
Reference gas flow, mL/min
Nitrogen
2
1
Pressure (psig)
(kPa)
Advanced User Guide
10
69
20
138
30
207
40
276
50
345
60
414
149
10 Detectors
20
16
Hydrogen
12
Makeup gas flow, mL/min
Helium
8
Nitrogen
4
Pressure (psig)
(kPa)
10
69
20
138
30
207
40
276
50
345
60
414
Selecting reference and makeup flows for the TCD
Table 23
Recommended flow rates and temperatures
Gas type
Flow range
Carrier gas
(hydrogen, helium, nitrogen)
Packed, 10 to 60 mL/min
Capillary, 1 to 5 mL/min
Reference
(same gas type as carrier)
15 to 60 mL/min
See the figures to select a value.
Capillary makeup
(same gas type as carrier)
5 to 15 mL/min—capillary columns
2 to 3 mL/min—packed columns
Detector temperature
<150 °C, cannot turn on filament
Detector temperature should be 30 °C to 50 °C greater than highest oven ramp
temperature.
Sample components with higher thermal conductivities than
the carrier gas produce negative peaks. For example, helium
or hydrogen form a negative peak with nitrogen or
argon- methane as the carrier gas.
Chemically active compounds reduce TCD filament life
The tungsten- rhenium TCD filament has been chemically
passivated to protect against oxygen damage. However,
chemically active compounds such as acids and halogenated
150
Advanced User Guide
Detectors
10
compounds may attack the filament. The immediate symptom
is a permanent change in detector sensitivity due to a
change in filament resistance.
If possible, such compounds should be avoided. If this is not
possible, the filament may have to be replaced frequently.
Changing the TCD polarity during a run
Negative polarity On inverts the peak so the integrator or
ChemStation can measure it. Negative polarity can be a run
table entry; see “Run Time Programming” on page 14.
Detecting hydrogen with the TCD using helium carrier gas
Hydrogen is the only element with thermal conductivity
greater than helium, and mixtures of small amounts of
hydrogen (<20%) in helium at moderate temperatures exhibit
thermal conductivities less than either component alone. If
you are analyzing for hydrogen with helium carrier gas, a
hydrogen peak may appear as positive, negative, or as a split
peak.
There are two solutions to this problem:
• Use nitrogen or argon- methane as carrier gas. This
eliminates problems inherent with using helium as carrier,
but causes reduced sensitivity to components other than
hydrogen.
• Operate the detector at higher temperatures—from 200 °C
to 300 °C.
You can find the correct detector operating temperature by
analyzing a known range of hydrogen concentrations,
increasing the operating temperature until the hydrogen peak
exhibits normal shape and is always in the same direction
(negative relative to normal response to air or propane)
regardless of concentration. This temperature also ensures
high sensitivity and linear dynamic range.
Because hydrogen peaks are negative, you must turn
negative polarity on at appropriate times so the peak
appears positive.
Advanced User Guide
151
10 Detectors
Setting parameters for the TCD
1 Press [Front Det] or [Back Det].
2
Set the detector temperature. Do not set higher than the
maximum temperature allowed for the column because part of
the column passes through the heated block and into the cell.
3
Verify that makeup gas type is the same as that plumbed
to your instrument (next to Makeup line in the parameter
list). Change the gas type, if necessary.
4
Set the reference gas flow rate.
5
If you are using packed columns, turn off the makeup gas
(or proceed to step 6 and enter 2 to 3 mL/min, see “TCD
carrier, reference, and makeup gas” on page 148) and
proceed to step 7
6
If you are using capillary columns:, choose a flow mode
and set the makeup gas flow or combined flow.
7
Turn on the filament. Allow about 30 minutes for thermal
stabilization. A longer period may be needed for the
highest sensitivity.
8
If necessary, turn Negative polarity [On/Yes] to invert
negative- going peaks. When a sample contains
components giving both positive- and negative- going
peaks, Negative polarity can be switched on and off during
a run as a timetable event.
Example: Packed mode (packed and large capillary columns)
Column flow is 15 to 60 mL/min. Set the reference flow to
1.5 times the sum of column flow + makeup flow.
Makeup gas is recommended with all capillary columns. It
allows the column to be inserted all the way into the
detector and withdrawn 1 mm. If makeup is not used, the
column must be no more than 3 mm above the ferrule.
Minimum makeup flow is 1 mL/min.
1/8-inch stainless steel column If column flow is 30 mL/min,
set the reference flow to 30 × 1.5 = 45 mL/min. Total
detector flow is 30 + 45 = 75 mL/min.
10 m × 0.53 mm column If column flow is 15 mL/min and
makeup flow = 2 mL/min, set the reference flow to 1.5 × (15
+ 2) = 25.5 mL/min. Total detector flow is 17 + 25.5 =
42.5 mL/min.
152
Advanced User Guide
Detectors
10
Example: Capillary mode (small capillary columns)
If combined column plus makeup flow is between 5 and
10 mL/min, set the reference flow at 3× the combined flow.
For a combined flow between 10 and 15 mL/min, use a
multiplier of 2. This will bring the TCD within 25% of the
maximum response. For further optimization, adjust the
reference flow.
2 m × 0.2 mm capillary column If column flow is 0.75 mL/min,
the makeup must be at least 4.25 mL/min. Set it = 5.
Reference flow will then be 3 × 5.75 = 17.25 mL/min. Total
detector flow = 5.75 + 17.25 = 22.5 mL/min.
25 m × 0.32 mm capillary column If column flow = 10 mL/min,
set makeup low to minimize sample dilution. Set it =
2 mL/min. Reference flow will then be 12 × 2 = 24 mL/min.
Total detector flow = 12 + 24 = 36 mL/min.
Advanced User Guide
153
10 Detectors
About the uECD
The micro- cell detector (uECD) contains a cell plated with
63Ni, a radioactive isotope. The 63Ni releases β particles that
collide with carrier gas molecules to produce low- energy
electrons—each β particle produces approximately 100
electrons. The free electrons produce a small current—called
the reference or standing current—that is collected and
measured in a pulsed circuit.
When a sample component molecule comes into contact with
the free electrons, the electrons may be captured by the
sample molecules to create negatively charged ions. The
voltage across the cell electrodes is pulsed to collect the
remaining free electrons while the heavier ions are relatively
unaffected and swept out the vent with the carrier gas flow.
Cell current is measured and compared to a reference
current. The pulse rate is adjusted to maintain a constant
cell current. The more uncaptured electrons, the lower the
pulse frequency required to match the reference current.
When a component that captures electrons passes through
the cell, the pulse rate rises. This pulse rate is converted to
a voltage and recorded.
uECD safety and regulatory information
The 63Ni isotope
The radioactive isotope used in the cell is 63Ni. It is plated
onto the inner surface of the cell body and is solid at
temperatures used in chromatography. Some other properties
are listed below.
Table 24
154
Properties of 63Ni
Property
Value
Half–life:
101.1 years
Emission:
65.87 keV max., beta radiation
Melting point:
1453 °C
Dimensions of the active part of the
uECD:
Inside diameter: 6 mm
Height: 4.2 mm
Total activity (uECD cell):
555 MBq (15 millicuries) maximum
Advanced User Guide
Detectors
10
uECD licenses
Customers in the United states can purchase an exempt
model uECD. Customers outside the United States should
contact their local Agilent sales office for information.
uECD warnings
Although beta particles at this energy level have little
penetrating power —the surface layer of the skin or a few
sheets of paper will stop most of them—they may be
hazardous if the isotope is ingested or inhaled. For this
reason the cell must be handled with care: Radioactive leak
tests must be performed at the required intervals (not
applicable to exempt models), the inlet and outlet fittings
must be capped when the detector is not in use, corrosive
chemicals must not be introduced into the detector, and the
effluent from the detector must be vented outside the
laboratory environment.
WA R N I N G
WA R N I N G
Materials that may react with the 63Ni source, either to form
volatile products or to cause physical degradation of the plated
film, must be avoided. These materials include oxidizing
compounds, acids, wet halogens, wet nitric acid, ammonium
hydroxide, hydrogen sulfide, PCBs, and carbon monoxide. This list
is not exhaustive but indicates the kinds of compounds that may
cause damage to 63Ni detectors.
In the extremely unlikely event that both the oven and the detector
heated zone should go into thermal runaway (maximum,
uncontrolled heating in excess of 400 °C) at the same time, and
that the detector remains exposed to this condition for more than
12 hours, take the following steps:
• After turning off the main power and allowing the
instrument to cool, cap the detector inlet and exhaust
vent openings. Wear disposable plastic gloves and observe
normal laboratory safety precautions.
• Return the cell for exchange, following directions included
with the License Verification Form (part no.
19233- 90750).
Advanced User Guide
155
10 Detectors
• Include a letter stating the condition of abuse.
It is unlikely, even in this very unusual situation, that
radioactive material will escape the cell. However, permanent
damage to the 63Ni plating within the cell is possible, and
therefore, the cell must be returned for exchange.
WA R N I N G
Do not use solvents to clean the uECD.
WA R N I N G
You may not open the uECD cell unless authorized to do so by your
local nuclear regulatory agency. Do not disturb the four
socket-head bolts. These hold the cell halves together. United
States customers removing or disturbing them is a violation of the
terms of the exemption and could create a safety hazard.
Safety precautions when handling uECDs
• Never eat, drink, or smoke when handling uECDs.
• Always wear safety glasses when working with or near
open uECDs.
• Wear protective clothing such as laboratory jackets, safety
glasses, and gloves, and follow good laboratory practices.
Wash hands thoroughly with a mild non- abrasive cleaner
after handling uECDs.
• Cap the inlet and outlet fittings when the uECD is not in
use.
• Connect the uECD exhaust vent to a fume hood or vent it
to the outside. See the latest revision of title 10, Code of
Federal Regulations, part 20, (including appendix B) or
the applicable State regulation. For other countries,
consult with the appropriate agency for equivalent
requirements.
Agilent Technologies recommends a vent line inside
diameter of 6 mm (1/4 inch) or greater. With a line of
this diameter, the length is not critical.
156
Advanced User Guide
Detectors
10
uECD gas flows
Anode purge
Makeup
EPC Module
Frit
Frit
Frit
Valve
Valve
Valve
Vent
PS
PS
Frit
63Ni
PS
Frit
Capillary adapter
Column
PS = Pressure Sensor
uECD linearity
The uECD response factor versus concentration curve is
linear for four orders of magnitude or more (linear dynamic
range = 104 or higher) for a broad range of compounds. You
should still run a calibration curve on your samples to find
the limits of the linear range for your materials.
uECD detector gas
The uECD operates with either nitrogen or argon/methane as
the makeup and anode gas. Purity is critical; gases must
exceed 99.9995% purity.
Because of the high detector sensitivity, carrier and makeup
gas must be dry and oxygen- free. Moisture, chemical, and
oxygen traps in good condition should be installed in carrier
and makeup gas supply lines. Do not use plastic (including
PTFE) tubing, plastic- bodied traps, or O- ring seals.
Advanced User Guide
157
10 Detectors
uECD temperature
To prevent peak tailing and to keep the cell clean, the
detector temperature should be set higher than the highest
oven temperature used—the setpoint should be based on the
elution temperature of the last compound. If you operate at
excessively high temperatures, your results will not
necessarily improve and you may increase sample and
column decomposition.
uECD analog output
If you intend to use the analog output from the uECD, you
must set the output Range to 10.
1 Press [Analog Out 1] or [Analog Out 2].
2 Scroll to Range.
3 Type 10 and press [Enter].
Recommended starting conditions for new uECD methods
Use the following information when selecting temperatures
and flows. Maximum source pressure must not exceed 100
psi. Use the maximum source pressure to achieve maximum
makeup flow rate.
Table 25
Starting values
Gas
Carrier gas
Packed columns
(nitrogen or argon-methane)
Capillary columns
(hydrogen, nitrogen, or
argon-methane)
Capillary makeup
(nitrogen or argon-methane)
Recommended flow range
30 to 60 mL/min
0.1 to 20 mL/min,
depending on diameter
10 to 150 mL/min
(30 to 60 mL/min typical)
Temperature
250 °C to 400 °C
Detector temperature is typically set 25 °C greater than the highest oven ramp
temperature.
158
Advanced User Guide
10
Detectors
uECD makeup gas notes
If the carrier gas type is different from the makeup gas type,
the makeup gas flow rate must be at least three times the
carrier gas flow rate.
uECD sensitivity can be increased by reducing the makeup
gas flow rate.
uECD chromatographic speed (for fast peaks) can be
increased by increasing the makeup gas flow rate.
uECD temperature programming
The uECD is flow sensitive. If you are using temperature
programming, in which the column flow resistance changes
with temperature, set up the instrument as follows:
• Set the carrier gas in the Constant flow mode. Set detector
makeup gas to Constant makeup.
• If you choose to work in the constant pressure mode, the
makeup gas should be set in the Column +makeup=constant
mode.
Setting parameters for the uECD
Verify that your detector gases are connected, a column is
properly installed, and the system is free of leaks. Set the
oven temperature and the inlet temperature and flow. Make
sure your carrier gas type is the same as that plumbed to
your GC.
1 Press [Front Det] or [Back Det].
2
Set the detector temperature. To keep the uECD cell
clean, this temperature must be higher than the oven
temperature.
3
Verify that the makeup gas type is the same as that
plumbed to your instrument. The gas type is in
parentheses next to the Makeup line on the parameter
list. Change the gas type, if necessary.
4
Enter a value for the makeup gas flow.
• If you are using packed columns, turn off the makeup
gas.
• If your capillary column is defined, choose a flow mode
and set the makeup or combined gas flow.
• If your capillary column is not defined, only constant
makeup flow is available. Enter a makeup gas flow.
Advanced User Guide
159
10 Detectors
About the NPD
We strongly recommend that you allow the firmware to
perform Auto Adjust and set the Bead Voltage.
NPD flows and general information
The NPD passes sample and carrier through a hydrogen/air
plasma. A heated ceramic or glass source, called the bead, is just
above the jet. The low hydrogen/air ratio cannot sustain a flame,
minimizing hydrocarbon ionization, while the alkali ions on the
bead surface facilitate ionization of nitrogen- or
phosphorus- organic compounds. The output current is
proportional to the number of ions collected. It is sensed by an
electrometer, converted to digital form, and sent to an output
device.
H2
Makeup
Frit
Frit
Valve
Valve
Air
EPC Module
Frit
Valve
Vent
PS
PS
Restrictor
PS = Pressure Sensor
160
PS
Electrically
heated bead
Restrictor
Restrictor
Column
Advanced User Guide
10
Detectors
NPD flow, temperature, and bead recommendations
Table 26
General operating values
Gas or Setting
Recommendation
Carrier gas (helium, hydrogen, nitrogen) Capillary, choose optimum flow
based on column dimensions.
Detector gases
Hydrogen
Ceramic bead
2 to 5 mL/min
Air
Ceramic bead
60 mL/min
Capillary makeup (helium, nitrogen)
Ceramic bead
Nitrogen: 5 to 10 mL/min
Helium: less than 5 mL/min
Temperature
Default is 250 °C; operating range is 150 °C to 400 °C.
• <150 °C, the Adjust offset process will not start.
• 325 to 335 °C is recommended.
• Detector temperature should be greater than the highest oven temperature.
With higher detector temperatures, less bead heating voltage is required.
Adjust offset
Default is 30 pA, suggested operating range is 20 to 40 pA, and allowable range
is 0 to 99.9 pA.
• ≥ 50 pA increases sensitivity but reduces bead life.
• Lower settings reduce sensitivity and increase bead life, but settings too low
will result in solvent quenching.
• The time required for Adjust offset depends on the bead type and condition.
Bead voltage
Ceramic bead. Range is 0 to 4.095 V.
• Use Auto Adjust On, Dry Bead, and let the GC set the Bead Voltage for you.
Source gas pressures
Choose a flow, find a pressure, and set source pressure
10 psi (70 kPa) higher.
Advanced User Guide
161
10 Detectors
150
Air
100
Flow, mL/min
Helium
50
Nitrogen
Pressure (psig)
(kPa)
5
10
69
20
138
30
207
40
276
50
345
60
414
70
483
4
Hydrogen
3
Flow, mL/min
2
1
Pressure (psig)
(kPa)
4
28
8
55
12
83
16
110
20
138
Temperature programming
The NPD is flow sensitive. If you are using temperature
programming, in which the column flow resistance changes
with temperature, set up the instrument as follows:
• Set the carrier gas in the Constant flow mode. Set detector
makeup gas to Constant makeup.
• If you choose to work in the constant pressure mode, the
makeup gas should be set in the Column +makeup=constant
mode.
NPD required gas purity
Because of its high sensitivity, the NPD requires very pure
(at least 99.9995%) gases. We strongly recommend that
moisture and organics traps be used on the carrier gas and
162
Advanced User Guide
Detectors
10
all detector gases, including the detector hydrogen, air, and
makeup gases. Do not use plastic (including PTFE) tubing,
plastic- bodied traps, or O- ring seals.
Setting parameters for the NPD
Before operating the NPD, make sure that detector gases are
connected, a column is installed, and the system is free of
leaks. Set the oven temperature, inlet temperature, and
column flow.
WA R N I N G
Make sure that a column is installed or the NPD column fitting is
plugged before turning on the air or hydrogen. An explosion may
occur if air and hydrogen are allowed to leak into the oven.
1 Select the bead (white ceramic, black ceramic).
2
Select the jet.
3
Install bead and jet as required. (See the Maintenance
Manual for details.)
4
Press [Config][Front Det] or [Config][Back Det].
5
If you are using makeup gas, verify that the configured
makeup gas type is the same as that plumbed to your
instrument. Change the gas type, if necessary. Nitrogen is
recommended.
6
If the displayed Bead Type is incorrect, set the Bead Type
using the [Mode/Type] key.
7
Set Auto Adjust (On recommended).
8
Set Dry Bead (On recommended).
9
Press [Front Det] or [Back Det].
10 Set the detector temperature. The recommended range is
325 to 335 °C.
11 Enter a hydrogen flow (3.0 mL/min is recommended).
Turn the flow On.
12 Enter an air flow (60 is recommended for ceramic beads).
Turn the flow On.
a If you are using packed columns, turn off makeup gas
and proceed to step 13.
b If your capillary column is defined, choose a flow
mode and set the makeup gas flow. For a column in
the constant flow mode, choose Constant makeup. For a
Advanced User Guide
163
10 Detectors
column in the constant pressure mode, choose Column
+makeup=constant.
c If your column is not defined, enter a makeup gas
flow. Only constant flow is available.
13 Monitor the offset adjustment process.
a If Auto Adjust is On, the adjust offset process starts
automatically when the detector reaches setpoint. If
Auto Adjust is Off, the Bead Voltage will gradually go to
the last setpoint after the bead reaches setpoint
temperature and the Dry Bead time has elapsed.
b If you need to set a new target offset, enter an Adjust
offset value. Adjust offset starts when the detector
reaches setpoint.
c If Auto Adjust is Off, you can manually start the Adjust
offset process by scrolling to Adjust offset, then pressing
[On/Yes].
d If your standard operating procedures require that you
set the bead voltage directly, see “Setting NPD bead
voltage manually (optional)” on page 169.
Selecting an NPD bead type
Two beads are available:
Table 27
NPD beads
Bead type
Part number
Advantages
Disadvantages
White ceramic
G1534-60570
Standard
Phosphorus tails
Black ceramic
5183-2007
Durable, no
phosphorus
tailing
Lower nitrogen
sensitivity,
about 40%
Ceramic beads
164
Advanced User Guide
10
Detectors
Selecting an NPD jet
Open the oven door and locate the column connection fitting
at the base of the detector. It will look like either a capillary
optimized fitting or an adaptable fitting.
Adaptable fitting
Capillary optimized fitting
Detector fitting
Adapter
• If you have an application that tends to clog the jet, select
a jet with a wider tip id.
• When using packed columns in high column- bleed
applications, the jet tends to clog with silicon dioxide.
For capillary optimized fittings, select one of the following
from Table 28.
Table 28
Jets for capillary optimized fittings
Figure 3 ID
Jet type
Part number
Jet tip id
Length
1
Capillary with extended jet
(recommended)
G1534-80580
0.29 mm (0.011 inch)
51.5 mm
2
Capillary
G1531-80560
0.29 mm (0.011 inch)
43 mm
3
High-temperature
G1531-80620
0.47 mm (0.018 inch)
43 mm
51.5 mm
1
43 mm
2
43 mm
1
3
Figure 2
2
3
Capillary optimized NPD jets
For the adjustable NPD, select one of the following from
Table 29.
Advanced User Guide
165
10 Detectors
Table 29
Jets for adaptable fittings
Figure 4 ID
Jet type
Part number
Jet tip id
Length
1
Capillary with extended jet
(recommended)
G1534-80590
0.29 mm (0.11 inch)
70.5 mm
2
Capillary
19244-80560
0.29 mm (0.011 inch)
61.5 mm
3
Capillary, high-temperature
19244-80620
0.47 mm (0.018 inch)
61.5 mm
4
Packed
18710-20119
0.46 mm (0.018 inch)
63.6 mm
70.5 mm
1
61.5 mm
2
61.5 mm
3
1
63.6 mm
2
3
4
4
Figure 3
Adaptable NPD jets
To configure the NPD
In addition to the Ignore Ready and Makeup gas type, the NPD
requires the following configuration settings. Scroll to each
and enable/disable using [On/Yes] or [Off/No].
Auto Adjust Bead Recommended On. When On, the automatic
adjust offset process starts when the bead reaches the
temperature setpoint after having been turned off or cooled
below 150 °C. Auto adjust starts after Dry Bead hold time, if
enabled. Auto Adjust Bead uses the adjust offset feature to
protect the bead—especially new beads—by making sure that
the desired offset is obtained with the lowest possible bead
voltage. When Off, the bead voltage will rise as soon as the
Dry Bead time elapses, or as soon as the temperature
setpoint is reached if Dry Bead is off.
Dry Bead Recommended On. When On, the bead temperature
holds at 150 °C for 5 minutes before continuing to the
setpoint. This allows any condensation to evaporate and be
swept out of the detector.
166
Advanced User Guide
10
Detectors
Maximum Bead Voltage Display only. Shows the current
maximum bead voltage for the configured bead type (4.095 V
for ceramic beads).
Automatically adjusting NPD bead voltage
Agilent recommends using the Adjust offset feature to
automatically determine the lowest bead voltage needed to
give the desired response.
When the detector is turned on, the temperature rises at a
controlled rate.
• If Dry Bead is On, temperature holds at 150 °C for 5
minutes to drive off moisture, then continues to the
setpoint.
• If Dry Bead is Off, the temperature rises directly to the
setpoint.
When the temperature reaches the setpoint, the Bead Voltage
gradually rises until it produces the desired output.
Adjust offset
When you enter a value here, or press [On/Yes] to use the
stored value, detector gas flows turn on, the bead heats, and
the bead voltage adjusts until Output is stable and equal to
the entered value. There are five stages of Adjust offset.
Detector off When the detector is off, Adjust offset and Bead
voltage are Off and initial Output is displayed.
Detector on—detector temperature less than 150 °C. When you
enter an Adjust offset value or press [On], detector gases turn
on and the display blinks the Temp not ready message.
Detector on—waiting for oven and/or detector to reach temperature
setpoint and equilibrium. If the oven or detector is not at
setpoint, the display continues to blink the Temp not ready
message.
Detector on—Dry Bead On If Dry Bead is On, the temperature
rise holds at 150 °C for 5 minutes to remove moisture, then
continues to the setpoint.
Advanced User Guide
167
10 Detectors
Detector on—during adjust offset. When the detector and oven
temperatures reach setpoint and equilibrate, the Adjust
offset process begins. The bead voltage is slowly increased
until the output is close to the Adjust offset value. The display
blinks Detector Slewing.
Detector on and ready. When the Adjust offset value is reached,
the Adjust offset line reads Done and displays the offset target
setpoint. Your detector is on and ready. The display shows
the actual Bead voltage.
Setting NPD adjust offset on the clock table
You can use the Clock table feature to begin Adjust offset at a
specified time.
Aborting NPD adjust offset
Press [Delete] with the cursor on the Adjust offset line. This
cancels the adjustment without turning off the detector gases
and bead voltage.
Extending the NPD bead life
These actions, together with the automated heatup and
adjust procedures, can extend ceramic bead life considerably.
• Use the lowest practical Adjust offset value. This will result
in a lower Bead Voltage during operation.
• Run clean samples.
• Turn the bead off when not in use.
• Keep the detector temperature high (320 to 335 °C).
• Turn the hydrogen flow off during solvent peaks and
between runs.
Turning hydrogen off during a solvent peak
When using the NPD, the baseline shifts after a solvent peak
and can take some time to stabilize, especially with
chlorinated solvents. To minimize this effect, turn off the
hydrogen flow during the solvent peak and turn it back on
after the solvent elutes. With this technique, the baseline
recovers to its original value in less than 30 seconds. This
also extends the life of the bead. The hydrogen can be
turned on and off automatically as part of a Run Table. See
“Run Time Programming” on page 14.
168
Advanced User Guide
Detectors
10
Turning hydrogen off between runs
To extend bead life, turn off the hydrogen flow between
runs. Leave all other flows and the detector temperature on.
Turn on the hydrogen flow for the next run; the bead will
ignite almost immediately. The process can be automated
with Run Table entries.
Turning off the detector
CAUTION
If you turn Adjust offset [Off] at any time, the bead voltage,
hydrogen, and air flows all turn off.
Setting the initial bead voltage for new beads
Before you turn on the bead for the first time, manually set
its voltage to a safe value so that the new bead is not
destroyed.
1 Make sure Adjust Offset is turned Off.
2
After the temperature stabilizes at setpoint, set the initial
Bead Voltage, depending on bead type:
• Ceramic bead (white or black): 0.0 V to 2.0 V
Setting NPD bead voltage manually (optional)
Bead voltage shows the voltage used to heat the bead. It can
be a value derived from the Adjust offset value, or can be
entered as a setpoint. Entering a setpoint causes the voltage
to change at 13 mV/second until it reaches the setpoint
provided that
• the detector is at the temperature setpoint
• temperature is at least 150 °C
• gas flows are on
• Dry Bead time, if On, has elapsed
Bead voltage is also useful for small adjustments between
runs. If you observe a baseline drift, you can enter a small,
one- time change to compensate for the drift.
If you are not using the recommended Adjust offset process,
note that large voltage jumps reduce bead life. Use
increments no greater than 0.05 V, spaced 10 seconds apart,
until you reach the desired offset.
Advanced User Guide
169
10 Detectors
New beads
After a new bead reaches the initial voltage, begin to
increase the voltage value in 0.05 V increments until the
bead ignites. Wait about 10 seconds between each voltage
adjustment. Monitor the detector output. When the bead
ignites, the output will rise suddenly, then decrease towards
a more stable value. It is best to allow the NPD to remain in
this state without further adjustment for about 24 hours.
Then you may adjust the bead voltage in small increments
(0.05 to 0.1 V) until reaching the desired offset. With a clean
environment, clean gas supplies, and low bleed column, a
typical offset may decrease 6- 12 pA during a 24 hour
period.
Typical voltages for new ceramic beads range from 2.5 to
3.7 volts. Higher values reduce bead life.
170
Advanced User Guide
Detectors
10
About the FPD
The sample burns in a hydrogen- rich flame, where some
species are reduced and excited. The gas flow moves the
excited species to a cooler emission zone above the flame
where they decay and emit light. A narrow bandpass filter
selects light unique to one species, while a shield prevents
intense carbon emission from reaching the photomultiplier
tube (PMT).
The light strikes a photosensitive surface in the PMT where
a light photon knocks loose an electron. The electron is
amplified inside the PMT for an overall gain of up to a
million.
H2
Makeup
Frit
Frit
Valve
Valve
Air
Frit
EPC Module
Vent
Valve
Emission Zone
PS
PS
PS
Restrictor
Wavelength filter
Window
Restrictor
PS = Pressure Sensor
Restrictor
Column
The current from the PMT is amplified and digitized by the
FPD electronics board. The signal is available either as a
digital signal on the communications output or as a voltage
signal on the analog output.
The FPD should not be stored at temperatures above 50 °C,
based on the original manufacturer’s specifications for the
PMT.
Advanced User Guide
171
10 Detectors
FPD linearity
Several mechanisms produce sulfur emission. The excited
species is diatomic, so that emission intensity is
approximately proportional to the square of the sulfur atom
concentration.
The excited species in the phosphorus mode is monatomic,
leading to a linear relationship between emission intensity
and atom concentration.
FPD Lit Offset
The default Lit Offset is 2.0 pA.
Starting Up and Shutting Down the FPD
The FPD creates a great deal of water vapor when the flame
is on. This could condense in the vent tube on top of the
detector and drop onto the flame, possibly extinguishing it.
To avoid this, turn the heaters on, wait 20 minutes for the
vent to heat up, and then ignite the flame. Water vapor will
now make it over the top of the vent tube before condensing.
For similar reasons, extinguish the flame before turning the
heaters off.
FPD photomultiplier protection
The PMT is extremely sensitive to light. Always turn the PMT
voltage off (which turns off the high voltage to the PMT)
before removing the PMT housing or opening the emissions
chamber. Failing to do this can destroy the PMT.
Even with the PMT voltage off, protect the PMT from room
light. Cap the housing when removed, place it end down to
exclude light, reduce room light level before exposing the
PMT, and so on. A brief exposure (always with the PMT
voltage turned off) will not damage it but prolonged exposure
will cause a gradual loss of sensitivity.
FPD optical filters
The filters are marked on the edge with the transmission
wavelength. Each filter has a small arrow on its side which
must point toward the PMT when installed.
The sulfur filter is silvery on both sides and transmits at
393 nanometers.
172
Advanced User Guide
10
Detectors
The phosphorus filter is yellow/green and transmits at
525 nanometers.
Inlet liners for use with the FPD
Compounds containing sulfur may adsorb on an inlet liner
and degrade the GC’s performance. Use deactivated, clean
liners or a cool on- column inlet, which injects directly onto
the column.
For best results with splitless injection, use liner 5181- 3316.
FPD temperature considerations
The minimum detector temperature to prevent water
condensation is 120 °C. We recommend a temperature that
is 25 °C higher than the highest column temperature, but no
higher than 250 °C.
FPD gas purity
High- purity gases have a lower sulfur content. Standard
purity gases have a higher sulfur content which impairs
sulfur detection in the compound being studied. Instrument
or Chromatographic grades work well.
Agilent recommends using helium carrier, nitrogen makeup
gas, and air with 99.9995% purity or better. Use carbon,
oxygen, and moisture traps. Select traps to remove sulfur
compounds from detector air and nitrogen gases. A helium
getter is also recommended.
FPD gas flows
Table 30 gives the flows for the maximum sensitivity FPD
flame, which is hydrogen- rich and oxygen- poor.
Table 30
Recommended flows
Sulfur mode flows,
mL/min
Phosphorus mode
flows, mL/min
Carrier (hydrogen, helium, nitrogen, argon)
Packed columns
10 to 60
10 to 60
Capillary columns
1 to 5
1 to 5
Detector gases
Advanced User Guide
173
10 Detectors
Table 30
Recommended flows (continued)
Sulfur mode flows,
mL/min
Phosphorus mode
flows, mL/min
Hydrogen
50
75
Air
60
100
Carrier + makeup
60
60
Helium, either as carrier or makeup gas, may cool the
detector gases below the ignition temperature. We
recommend using nitrogen rather than helium.
Lighting the FPD flame
Before trying to light the flame, have the detector at
operating temperature. Removing the condensate tubing may
help, but be sure to replace it before making runs.
It is difficult to light the flame with the flows shown in
Table 30, particularly in the sulfur mode. If the flame will
not light with the sulfur mode flows shown, change to the
phosphorus mode flows. After ignition, gradually reduce the
flows to the sulfur values. Some experimentation will be
needed.
When either of the flame ignition methods in this section is
used, the FPD automatically performs this sequence:
1 Turns all detector gases—air, hydrogen, makeup—off.
Carrier remains on.
2
Sets air flow to 200 mL/min.
3
Turns the glow plug ignitor on.
4
Ramps the hydrogen flow from 10 to 70 mL/min.
5
Resets the air flow to the air flow setpoint.
6
Resets the hydrogen flow to the hydrogen flow setpoint.
7
Turns the makeup gas on.
8
Compares the signal change with the Lit offset value. If the
change is greater than Lit offset, declares the flame on
(lit). If it is less, declares the flame off (not lit).
For this process to work, there must be enough air pressure
to the pneumatics module to provide 200 mL/min flow. We
recommend a supply pressure of 90 psi.
174
Advanced User Guide
Detectors
10
Manual ignition
1 Press [Front Det] or [Back Det].
2
Scroll to Flame. Press [On/Yes]. The flame ignition
sequence begins.
Automatic ignition
If the FPD output with the flame on falls below the
flame- off output plus the Lit offset value, this is interpreted
as a flame- out condition. The FPD runs the flame ignition
sequence to relight the flame. If this fails, it runs the
sequence again. If the second attempt also fails, the detector
shuts down all functions except temperature and makeup gas
flow.
Setting parameters for the FPD
WA R N I N G
Verify that a column is installed or the FPD fitting is plugged
before turning on the air or hydrogen. An explosion may occur if
air and hydrogen are allowed to leak into the oven.
1 Press [Front det] or [Back det].
2
Set the detector temperature. It must be greater than
120 °C for the flame to light.
3
Change the hydrogen flow rate, if desired. Press [Off/No].
4
Change the air flow rate, if desired. Press [Off/No].
5
If you are using packed columns, turn off the makeup gas
and proceed to step 7.
6
If you are using capillary columns:
a Verify that makeup gas type is the same as that
plumbed to your instrument (next to Makeup in the
parameter list). Change the gas type, if necessary.
b If your capillary column is defined, choose a flow
mode and set the makeup gas flow or combined flow.
c If your capillary column is not defined, enter a makeup
gas flow. Only constant flow is available.
7
Scroll to Flame and press [On/Yes]. This turns on the air
and hydrogen and initiates the ignition sequence.
On ignition, the signal increases. Typical levels are 4 to
40 pA in sulfur mode, 10 to 70 pA in phosphorus mode.
Verify that the flame is lit by holding a cold, shiny
Advanced User Guide
175
10 Detectors
surface, such as a mirror or chrome- plated wrench, over
the vent exit. Steady condensation indicates that the
flame is lit.
176
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
11
Valves
The Valve Box 178
Heating the valves 178
Valve temperature programming 178
Valve Control 179
The valve drivers 179
The internal valve drivers 179
Valve Types 181
Configuring a Valve 182
Controlling a Valve 183
From the keyboard 183
From the run or clock time tables 183
Gas sampling valve 183
Agilent Technologies
177
11 Valves
The Valve Box
The GC holds up to two valves in a heated valve box on top
of the oven.
The valve box is the preferred location for valves because it
is a stable temperature zone, isolated from the column oven.
Back of chromatograph
Valve heater block
Valve box, cover
removed
Figure 4
Diagram of valve locations on GC
Heating the valves
The valve box contains a heated block with two valve
mounting locations (shaded in Figure 4). The middle hole on
each block is used to pass tubing into the column oven.
If two valves are used, they share the same temperature
setpoint.
Valve temperature programming
Most valve applications are isothermal; however, you can
define three temperature ramps if desired. Program this
ramp the same as an oven ramp. Refer to “Setting the oven
parameters for ramped temperature” on page 132 for more
information.
178
Advanced User Guide
Valves
11
Valve Control
Valves can be controlled manually from the software
keyboard or as part of a clock or run time program. Note
that sampling valves automatically reset at the end of a run.
The valve drivers
A valve driver is the software and circuitry in the GC that
controls a valve or related function. There are two drivers,
known as Valve 1 and Valve 2. If a third valve is installed,
one of these two drivers controls two valves at the same
time.
Table 31
Valve drivers
Valve number
Type
Volts
Power or current
Use
1 and 2
Current source
24 VDC
13 watts
Pneumatic valve
control
The internal valve drivers
Valve drivers 1 through 2 are usually used to control
pneumatically operated valves mounted in the valve box. The
wiring for these appears at a set of connectors inside the
right cover of the GC.
Pneumatically driven valves are controlled by solenoids
mounted near the connectors that control the flow of air to
the valve actuators.
Keyboard
Connector
V1
or
Run table
Internal valve drivers
(1 and 2)
or
Clock table
Advanced User Guide
Connector
V2
179
11 Valves
There is no direct relationship between the location of a
valve in the valve box and the driver that controls it. This
depends on how the solenoids are wired and the actuators
are plumbed.
Manual valves must be switch by hand, and are heated or
unheated.
180
Advanced User Guide
Valves
11
Valve Types
There possible valve types are:
Sampling A two- position (load and inject) valve. In load
position, an external sample stream flows through an
attached (gas sampling) or internal (liquid sampling) loop
and out to waste. In inject position, the filled sampling loop
is inserted into the carrier gas stream. When the valve
switches from Load to Inject, it starts a run if one is not
already in progress. See the example on page 183.
Not installed
Advanced User Guide
Self- explanatory.
181
11 Valves
Configuring a Valve
1 Press [Config]. Scroll to Valve #.
182
2
Enter the valve number and press [Enter]. The current
valve type is displayed.
3
To change the valve type, press [Mode/Type], select the
new valve type, and press [Enter].
Advanced User Guide
11
Valves
Controlling a Valve
From the keyboard
Valves have two positions controlled by the [On] and [Off]
keys. The keyboard commands for two- position valves are:
[Valve #] <scroll to the valve> [On]
stop
Rotates valve to one
and
[Valve #] <scroll to the valve> [Off]
other stop
Rotates valve to the
From the run or clock time tables
The Valve On and Valve Off commands can be run time or clock
time programmed. See “Run Time Programming” on page 14
and “Clock Time Programming” on page 17.
If a valve is rotated by a run time program, it is not
automatically returned to its initial position at the end of
the run. You must program this reset operation yourself.
Gas sampling valve
If a valve is configured as a gas sampling valve, it starts a
run automatically when it is switched to the Inject position.
This can be done with a keyboard command or by a
subsequence or clock table entry. You may have two gas
sampling valves installed.
To column
Carrier in
LOAD position
INJECT position
Loop
Sample in
Sample out
Load position The loop is flushed with a stream of the
sample gas. The column is flushed with carrier gas.
Advanced User Guide
183
11 Valves
Inject position The filled loop is inserted into the carrier gas
stream. The sample is flushed onto the column. The run
starts automatically.
Carrier gas may be provided by an (optional) PCM channel.
To do this, configure the column and specify the PCM
channel as the inlet. The channel then becomes
programmable with four operating modes.
Sampling valves have two positions:
Load position The loop (external for gas sampling, internal
for liquid sampling) is flushed with a stream of the sample.
The column is flushed with carrier gas.
Inject position The filled loop is inserted into the carrier gas
stream. The sample is flushed onto the column. The run
starts automatically.
The sampling valve control parameters are:
Load time Time in minutes that the valve remains in the
Load position before becoming ready.
Inject time Time in minutes that the valve remains in the
Inject position before returning to the Load position.
The sampling valve cycle is:
1 The sampling valve rotates to the Load position. Load time
begins. Valve is not ready.
2
Load time ends. The valve becomes ready.
3
If everything else is ready, the GC becomes ready. If
anything is not ready:
• If you are using Clock Table or sequence control, the
GC waits until everything is ready, then executes the
valve inject command.
• If you are not using Clock Table or sequence control,
the valve injection can be made at any time from the
keyboard.
184
4
The sampling valve rotates (keyboard command or
sequence control) to the Inject position. Inject time begins.
The run begins.
5
Inject time ends. Return to step 1.
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
12
Cables
About Cables and Back Panel Connectors 186
Back panel connectors 186
Sampler connectors 186
Signal connector 186
REMOTE connector 187
TEST PORT connector 187
LAN connector 187
Using the Remote Start/Stop cable 188
Cable Diagrams 193
Analog cable, general use 193
Remote start/stop cable 193
Agilent Technologies
185
12 Cables
About Cables and Back Panel Connectors
Some parts of an analysis system are connected to the GC
by cables. These cables and the back panel connectors to
which they connect are described in this section.
Back panel connectors
These are the connectors on the back panel of the GC:
SIGNAL
LAN
LAN
TEST PORT
ALS Port Front
SAMPLER1
ALS Port Back
SAMPLER2
REMOTE
TEST PORT
Sampler connectors
If using an ALS, connect to the GC using the following
connectors:
ALS PORT Front
inlet.
An injector, typically mounted over the front
ALS PORT Back
inlet.
An injector, typically mounted over the back
Signal connector
The two analog output signal.
186
Advanced User Guide
Cables
12
REMOTE connector
Provides a port to remotely start and stop other
instruments. A maximum of 10 instruments can be
synchronized using this connector. See “Using the Remote
Start/Stop cable” on page 188 for more detail.
TEST PORT connector
This connector is reserved for future development.
LAN connector
Standard Local Area Network connector, for communication
with data systems and other devices.
Advanced User Guide
187
12 Cables
Using the Remote Start/Stop cable
Remote start/stop is used to synchronize two or more
instruments. For example, you might connect an integrator
and the GC so that the [Start]/[Stop] buttons on either
instrument control both of them. You can synchronize a
maximum of ten instruments using Remote cables.
Connecting Agilent products
If connecting two Agilent products with Remote cables, the
sending and receiving circuits will be compatible—just plug in
both ends of the cable.
Connecting non-Agilent products
If connecting to a non- Agilent product, the following
paragraphs contain information you will need to ensure
compatibility.
APG Remote signal electrical specifications
The APG signals are a modified open collector type. The
signal levels are generally TTL levels (low voltage is logic
zero, high voltage is logic one) but the open circuit voltage
will be between 2.5 and 3.7 Volts. The typical voltage is 3
Volts. A voltage over 2.2 volts will be interpreted as a high
logic state while a voltage below 0.4 volts will be interpreted
as a low logic state. These levels provide some margin over
the specifications of the devices used.
The pull- up resistance, connected to the open- circuit voltage,
is in the range of about 1K ohms to 1.5K ohms. For a
logic- low state, for a single device on the bus, the minimum
current you must be able to sink is 3.3 milliamps. Since
devices are connected in parallel, when you have multiple
devices this minimum current must be multiplied by the
number of devices attached on the bus. The maximum
voltage for a low- input state = 0.4V.
The bus is passively pulled high. Leakage current out of a
port must be less than 0.2 milliamps to keep the voltage
from being pulled lower than 2.2 volts. Higher leakage
current may cause the state to be interpreted as a low.
Over- voltage protection - APG Remote connections are
clamped by a zener diode to 5.6 Volts. Exceeding this voltage
will damage the circuit (main board).
188
Advanced User Guide
12
Cables
APG Remote - Suggested drive circuits
A signal on the APG bus may be driven by another APG
device or by one of the following circuits:
• A relay, with one side connected to ground, when closed
will set a logic- low state.
• An NPN transistor, with the emitter connected to ground
and the collector connected to the signal line will set a
logic- low state if proper base current is supplied.
• An open- collector logic gate will perform this same
function.
• A low- side drive IC will also work, but Darlington- type
drivers should be avoided as they will not meet the
low- side voltage requirement of less than 0.4V
APG Remote connector
Pin
1
5
6
9
Function
Logic
1
Digital ground
2
Prepare
LOW true
3
Start
LOW true (input)
4
Start relay
5
Start relay
6
not used
7
Ready
HIGH true (output)
8
Stop
LOW true
9
not used
APG Remote signal descriptions
Prepare (Low True) Request to prepare for analysis. Receiver
is any module performing pre- analysis activities. For
example, shorting pin 2 to ground will put the GC into Prep
Run state. This is useful for Splitless Mode to prepare the
inlet for injection or when using the Gas Saver. This function
is not needed by Agilent autosampler systems.
Ready (High True) If The Ready Line is high (> 2.2 VDC)
then the system is ready for next analysis. Receiver is any
sequence controller.
Advanced User Guide
189
12 Cables
Start (Low True) Request to start run/timetable. Receiver is
any module performing runtime- controlled activities. The
7820A GC requires a pulse duration of at least 500
micro- seconds to sense a start from an external device.
Start Relay (Contact Closure) A 120 millisecond contact
closure – used as an isolated output to start another device
that is not compatible or connected with APG Remote pin 3.
Stop (Low True) Request to reach system ready state as soon
as possible (for example, stop run, abort or finish, and stop
injection). Receiver is any module performing
runtime- controlled activities. Normally this line is not
connected, if the GC oven program is used to control the
method Stop time.
Prepare
System Ready
Waiting for Ready
Postrun
Runtime elapsed/Start
Run
Injection/Start
Injection cycle started
Start Requested
System Ready
Not Ready during Prep
Request for Prepare
System Ready
Waiting for Ready
APG Remote timing diagram
H
L
Start
H
L
Stop
H
L
H
Ready
190
H
H
L
Advanced User Guide
Cables
12
Connecting Cables
Connect a GC to an Agilent data system computer using
LAN communications using a LAN cable. See Figure 5 below.
LAN cable 8121-0940
or
Crossover LAN cable 5183-4648
LAN hub/switch
LAN cable
8121-0940
LAN cable
8121-0940
Computer
GC
Figure 5
Computer
GC
Connecting the GC and computer with a hub/switch (shown at left) or a crossover cable (shown at
right).
Table 32
Typical IP addresses for an isolated LAN
GC
Computer
IP address
192.168.0.26
192.168.0.1
Subnet mask
255.255.255.0
255.255.255.0
A single communications LAN cable is supplied with the GC.
The switch (or hub) and other cables must be ordered
separately, if needed. See Table 32 and Table 33 for cabling
requirements for other configurations.
Table 33
Advanced User Guide
Cabling requirements
7820A GC connected to:
Required Cable(s)
Part number
7693A Automatic Liquid
Sampler
Injector cable
G4514-60610
7697A Headspace
Sampler
Remote, 9-pin
male/6-pin connector
G1530-60930
3395B/3396C Integrator
Remote, 9 pin/15 pin
Analog, 2 m, 6 pin
03396-61010
G1530-60570
Non-Agilent
Integrator
General purpose analog
signal cable
2 m, 6 pin
G1530-60560
191
12 Cables
Table 33
192
Cabling requirements (continued)
7820A GC connected to:
Required Cable(s)
Part number
Non-Agilent
data system
General use remote,
9-pin male/spade lugs
(various lengths)
35900-60670 (2 m),
35900-60920 (5 m),
35900-60930 (0.5 m)
LAN
Cable, networking CAT 5, 8121-0940
25 feet
Cable, LAN, crossover
5183-4648
Advanced User Guide
Cables
12
Cable Diagrams
Analog cable, general use
Connector 1
Connector 2
The pin assignments for the general use analog out cable are
listed in Table 34.
Table 34
Analog cable, general use, output connections
Connector 1
Connector 2, wire color
Signal
1
Brown or violet
Not used
2
White
0 to 1 V, 0 to 10 V (–)
3
Red
Not used
4
Black
1 V (+)
6
Blue
10 V (+)
Shell
Orange
Ground
Remote start/stop cable
Connector 1
Connector 2
The pin assignments for the remote start/stop cable are
listed in Table 35.
Advanced User Guide
193
12 Cables
Table 35
194
Remote start/stop cable connections
Connector 1, 9-pin male
Connector 2, wire color
Signal
1
Black
Digital ground
2
White
Prepare (low tone)
3
Red
Start (low tone)
4
Green
Start relay (closed during
start)
5
Brown
Start relay (closed during
start)
6
Blue
Open circuit
7
Orange
Ready (high true input)
8
Yellow
Stop (low tone)
9
Violet
Open circuit
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
13
GC Output Signals
About Signals 196
Analog Signals 197
Analog zero 197
Analog range 197
Analog data rates 198
Selecting fast peaks (analog output) 199
Digital Signals 200
Digital zero 200
Signal Freeze and Resume 200
Data rates with Agilent data systems 201
Agilent Technologies
195
13 GC Output Signals
About Signals
Signal is the GC output to a data handling device, analog or
digital. It can be a detector output or the output from flow,
temperature, or pressure sensors. One signal output channel
is provided.
Signal output can be either analog or digital, depending on
your data handling device. Analog output is available at
either of two speeds, suitable to peaks with minimum widths
of 0.004 minutes (fast data rate) or 0.01 minutes (normal
rate). Analog output ranges are 0 to 1 V, 0 to 10 V, and 0 to
1 mV.
Digital output rates are set by your Agilent data system,
such as ChemStation or EZChrom.
See Table 36 for the conversions from units shown on the
GC display to units as shown in Agilent data systems and
integrators.
Table 36
Signal type
Signal conversions
1 display unit is equivalent to:
Detector:
FID, NPD
1.0 pA (1.0 × 10-12 A)
TCD
25 uV (2.5 × 10-5 V)
µECD
1 Hz
Analog input board (use to connect the 15 µV
GC to non-Agilent detector)
196
Nondetector:
Thermal
1 °C
Pneumatic:
Flow
Pressure
Diagnostic
1 mL/min
1 pressure unit (psi, bar, or kPa)
Mixed, some unscaled
Advanced User Guide
GC Output Signals
13
Analog Signals
If you use an analog recorder, you may need to adjust the
signal to make it more usable. Zero and Range in the Signal
parameter list do this.
Analog zero
Zero Subtracts value entered from baseline. Press [On/Yes]
to set to current Value or [Off/No] to cancel.
This is used to correct baseline elevation or offsets. A
common application is to correct a baseline shift that occurs
as the result of a valve operation. After zeroing, the analog
output signal is equal to the Value line of the parameter list
minus the Zero setpoint.
Zero can be programmed as a run time event. For details, see
“Run Time Programming” on page 14.
1 Verify that the detector is on and in a ready state.
2
Press [Analog Out].
3
Scroll to Zero.
4
Press [On/Yes] to set Zero at the current signal value,
or
Enter a number between - 500000 and +500000. A value
smaller than the current Zero shifts baseline up.
Analog range
Range Scales data coming from the detector
Range is also referred to as gain, scaling, or sizing. It sizes
the data coming from the detector to the analog signal
circuits to avoid overloading the circuits (clamping). Range
scales all analog signals.
If a chromatogram looks like A or B in the next figure, the
data needs to be scaled (as in C) so that all peaks are
visible on the paper.
Valid setpoints are from 0 to 13 and represent 20 (=1) to 213
(=8192). Changing a setpoint by 1 changes the height of the
chromatogram by a factor of 2. The following chromatograms
illustrate this. Use the smallest possible value to minimize
integration error.
Advanced User Guide
197
13 GC Output Signals
A: Range = 0
B: Range = 3
C: Range = 1
There are limits to usable range settings for some detectors.
The table lists the valid range setpoints by detector.
Table 37
Range limits
Detector
Usable range settings (2x)
FID
0 to 13
NPD
0 to 13
FPD
0 to 13
TCD
0 to 6
υECD
0 to 6
Analog input
0 to 7
Range may be run time programmed. See “Run Time
Programming” on page 14 for details.
Analog data rates
Your integrator or recorder must be fast enough to process
data coming from the GC. If it cannot keep up with the GC,
the data may be damaged. This usually shows up as
broadened peaks and loss of resolution.
Speed is measured in terms of bandwidth. Your recorder or
integrator should have a bandwidth twice that of the signal
you are measuring.
The GC allows you to operate at two speeds. The faster
speed allows minimum peak widths of 0.004 minutes (8 Hz
bandwidth), while the standard speed allows minimum peak
widths of 0.01 minutes (1.6 Hz bandwidth).
If you use the fast peaks feature, your integrator should
operate at around 15 Hz.
198
Advanced User Guide
GC Output Signals
13
Selecting fast peaks (analog output)
1 Press [Config][Analog Out].
2
Scroll to Fast peaks and press [On].
Agilent does not recommend using Fast peaks with a thermal
conductivity detector. Since the gas streams switch at 5 Hz,
the gain in peak width is offset by increased noise.
Advanced User Guide
199
13 GC Output Signals
Digital Signals
The GC outputs digital signals only to an Agilent data
system. The following discussions describe features that
impact the data sent to data systems, not the analog data
available to integrators. Access these features from the
data system. These features are not accessible from the
GC keypad.
Digital zero
Available only from an Agilent data system.
Digital signal outputs respond to a zero command by
subtracting the signal level at the time of the command from
all future values.
Signal Freeze and Resume
Available only from an Agilent data system.
Some run time operations, such as changing signal
assignments or switching a valve, can cause baseline upsets.
Other factors can cause baseline upsets also. The GC can
compensate for this by pausing (freezing) the signal at a
particular value, using that signal value for a specified
duration, and then resuming normal signal output.
Consider a system that uses a switching valve. When the
valve switches, an anomaly occurs in the baseline. By
freezing and resuming the signal, the anomaly can be
removed so that the peak identification and integration
software operates more smoothly.
200
Advanced User Guide
13
GC Output Signals
Baseline upset due to valve switch
Pause signal here
Resume signal here
Data rates with Agilent data systems
The GC can process data at various data rates, each
corresponding to a minimum peak width. The table shows
the effect of data rate selection.
Table 38
Advanced User Guide
EZChrom/ChemStation data processing
Data rate, Hz
Minimum peak
width, minutes
Relative
noise
Detector
Column type
500
0.0001
5
FID
Narrow-bore,
0.05 mm
200
0.001
3.1
FID
Narrow-bore,
0.05 mm
100
0.002
2.2
FID/NPD only
Capillary
50
0.004
1.6
20
0.01
1
10
0.02
0.7
201
13 GC Output Signals
Table 38
EZChrom/ChemStation data processing (continued)
Data rate, Hz
Minimum peak
width, minutes
Relative
noise
5
0.04
0.5
2
0.1
0.3
1
0.2
0.22
0.5
0.4
0.16
0.2
1.0
0.10
0.1
2.0
0.07
Detector
Column type
to
All types
Slow packed
You cannot change the data rate during a run.
You will see higher relative noise at the faster sampling
rates. Doubling the data rate can double peak height while
the relative noise increases by 40%. Although noise increases,
the signal- to- noise ratio is better at the faster rates.
This benefit only occurs if the original rate was too low,
leading to peak broadening and reduced resolution. We
suggest that rates be chosen so that the product of data rate
and peak width in seconds is about 10 to 20.
The figure shows the relationship between relative noise and
data rates. Noise decreases as the data rate decreases until
you get to data rates of around 5 Hz. As the sampling rate
slows, other factors such as thermal noise increase noise
levels.
202
Advanced User Guide
GC Output Signals
Relative noise level
13
Excess noise (due to flow,
oven temperature, detector
block temperatures, etc.)
Faster data rates
Slower data rates
Zero Init Data Files
This feature applies to digital output only, and is mainly
intended for non- Agilent data systems. It may help systems
that have trouble with non- zero baseline output.
When you turn it On, the GC immediately begins to subtract
the current detector output value(s) from any future values.
For example, if you turn it on when the output is 20 pA, the
GC subtracts 20 pA from the digital output until you turn
Zero Init Data Files Off.
You will not see any change in the GC display, but you will
see the change in the online plot available in the data
system.
To change this setting, press [Config], scroll to Instrument,
then scroll to Zero Init Data Files.
Advanced User Guide
203
13 GC Output Signals
204
Advanced User Guide
Agilent 7820A Gas Chromatograph
Advanced User Guide
14
Miscellaneous Topics
About Pressure Control 206
Pressure units 206
To Use the Stopwatch 207
Service Mode 208
Service Reminders 208
Other functions 208
Agilent Technologies
205
14 Miscellaneous Topics
About Pressure Control
Pressure units
There are two common ways of expressing gas pressures:
psia
Absolute pressure, measured relative to vacuum.
psig Gauge pressure, measured relative to atmospheric
pressure. This name is used because most pressure gauges
have one side of the sensing element exposed to the
atmosphere.
The two measurements are related by:
psia = psig + atmospheric pressure
206
Advanced User Guide
14
Miscellaneous Topics
To Use the Stopwatch
In the stopwatch mode, both the time (to 0.1 second) and
reciprocal time (to 0.01 min- 1) are displayed. The stopwatch is
useful when measuring flows with a bubble flowmeter.
1 Press [Time] and scroll to the time = line.
2
Press [Enter] to start the stopwatch.
3
Press [Enter] again to stop.
4
Press [Clear] to set to zero.
You can access other functions while the stopwatch is
running. Press [Time] again to view the stopwatch display.
Advanced User Guide
207
14 Miscellaneous Topics
Service Mode
The [Service Mode] key presents the Service Reminders and
other functions.
Service Reminders
Internal counters
This is a set of 12 counters that monitor the use of various
items on the GC, such as syringes, septa, and columns.
These counters only count runs and their definitions are
fixed. You can set limits for each item; when a limit is
reached, the Service Due light on the status board comes on.
Examine the limits to identify the item that has reached its
limit.
You may enter a limit for each item, reset a count to 0 by
pressing [Off/No], or disable a counter by entering a limit of
0.
The counter limits in Table 39 are recommendations. Adjust
the limits as needed to fit your needs.
Table 39 Recommended initial counter limits
Counter
Recommended Limit
Syringe 1 and 2
1000 injections
Septum, Front and Back
150 injections for 7693A ALS
2000 injections if using the Merlin Micro Seal
Liner, Front and Back
Sample and method dependent. Depending on the sample type, the liner may
need to be replaced daily, weekly, or monthly.
In some cases, septum chunks get in the liner. You may want to match the
septum counter, or set the liner counter to a multiple of 2 or 3 times the septum
counter.
Columns 1-6
Sample and method dependent. Depending on the sample type, columns may
need to be replaced after 50 injections, or they may last through thousands of
injections.
Other functions
These are for use by trained Agilent personnel. They are
described in the Service Manual.
208
Advanced User Guide
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement