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Analytical & Bioanalytical
Techniques
Zhao, J Anal Bioanal Tech 2014, S12
http://dx.doi.org/10.4172/2155-9872.S12-008
Open Access
Review Article
Development of an On-line GC System using Existing Retired Equipment
Yuhui (Henry) Zhao*
EPCOR Utilities Inc., Edmonton, Alberta, Canada
Abstract
To ensure drinking water quality, continual monitoring of the volatile organic compounds (VOCs) in the source
water and the treated water is very important for any water treatment plant. On-line, real-time information is crucial to
water treatment engineers and operators. The concentration of VOCs provides such information. For VOCs analysis,
gas chromatography (GC) is one of the best techniques due to its high sensitivity and selectivity. As a result, an inhouse on-line GC System was developed for this purpose at a water treatment plant. It included the following parts: a
stream selection device to connect two sample streams; a self-cleaning filter to remove sands and suspended solids;
a Purge-and-Trap (P&T) device to extract and concentrate the volatile compounds; a GC (from Hewlett-PackardTM)
equipped with a Flame Ionization Detector (FID) to identify and quantify the compounds; a computer with WindowsTM
XP plus ChemStation to control the sampling valves through a DAQ (from National InstrumentsTM) and to control the
GC and P&T through a GPIB-USB interface (from AgilentTM). To minimize cost in the development of this system,
shelved GC and P&T were used. These instruments have been retired from regular use but still in good working
condition.
Keywords: On-line; GC; Purge-and Trap; Water treatment
Introduction
There is no doubt that drinking water safety is of the ultimate
importance for general public, water treatment plants and drinking
water distributors. To monitor the drinking water quality, an on-line
GC was developed in our laboratory with existing retired equipment.
Volatile Organic Compounds (VOCs), along with other possible
contaminants affect the taste of the drinking water and may present
a health risk if it exceeds the acceptable level [1]. For example,
disinfection products such as Trihalomethanes (THMs) are one of
these VOC groups. The generation of these by-products greatly depend
on the amount of available organic carbon in the raw water. Therefore,
decisions for the treatment processes and chemical doses are often
based on the quality of raw water [2]. As a drinking water provider, it is
necessary to monitor the water quality, including the VOC level, before,
during, and after the water treatment process.Monitoring of VOCs can
be done by repeatedly taking samples and analyzing them 24 hours a
day, all year around, but it is more efficient to put an instrument in the
production line, let the instrument take the sample, finish the analysis,
and automatically report the results to the operator and the quality
assurance personnel. To do this, an on-line system is required.
To meet the requirements of water quality guidelines from relevant
Transfer line
Trap
For those organizations willing to invest large amount of money in
analytical equipment, there is commercial on-line GC system available
on the market, for instance by WASSONTM Instruments. However, it is
a relatively big financial investment to purchase, install and operate. In
this paper, a built- in-house unit using retired equipment is described.
The derivation of the equipment selection is as follows: The
GC with FID
FID
Helium
Purging gas
The basic principle and operation of these instruments can be found
in the user’s manuals [4,5] and is illustrated in Figure 1. Briefly, a water
sample is introduced in the sparger on the P&T device, and the VOCs
(analytes) are extracted from the water matrix by bubbling a steady flow
of helium through the aqueous sample. The purged organic compounds
are trapped and concentrated onto an absorbent trap. The analytes
are then released by heating the trap onto the head of the column in a
GC instrument. A stream of carrier gas (usually helium or hydrogen)
flowing through the column under a predefined temperature program
separate and elute the compounds from the column. The compounds
eluted from the column reach the FID and are then identified by their
retention times by comparing to the calibration standards. Quantitation
is achieved by a standard calibration.
Equipment Selected for this Project
Helium
Carrier gas
Purge & Trap
jurisdictions, low detection limits are required for most of the measured
organic compounds. The most common method of measuring VOCs
in water samples is Purge-and-Trap (P&T) coupled with a Gas
Chromatography with Flame Ionization Detector (GC-FID) [3]. This
is mainly due to its high resolution, simplicity, reliability, wide linear
range, and relatively high sensitivity. This project uses this technique.
GC column
*Corresponding author: Yuhui (Henry) Zhao, EPCOR Utilities Inc., Edmonton,
Alberta, T5K 0A5, Canada, Tel: 780-412-7612; E-mail: YZHAO@epcor.com
Received November 22, 2013; Accepted February 28, 2014; Published March
04, 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing
Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/2155-9872.S12008
Sparger
Figure 1: Schematic diagram showing the principle of a P&T system with a
GC- FID system.
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Copyright: © 2014 Zhao YH. This is an open-access article distributed under the
terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and
source are credited.
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 2 of 8
Device
(new or used)
Model
Features
Reference
GC (used)
HP5890 II
GPIB interface;
Remote control ready;
FID;
DB 624 column;
Chemstation control or stand alone
[4]
Purge & Trap (used)
LSC 3100
Hand held device control or computer control;
Single sample or scheduled run possible.
[5]
MW S150-24
Input:110 – 120 VAC 3.2 A ;
Output: +24 VDC 6.5 A
[8]
Solenoid V1 (used)
ASCO Redhat II
3 way;
24VDC, 11.6W;
Pressure limit 100 psi
[8]
Solenoid V3 (used)
ASCO Redhat II
3 way;
24VDC, 11.6W;
Pressure limit 100 psi
[8]
Solenoid V4 (used)
ASCO Redhat
2 wayNC;
12-24VDC, 2W;
Pressure limit 100 psi
[9]
NI DAQ (new)
USB 6525
Individual relays built in;
8 Isolated Digital Input channels +/- 60V DC ;
8 Isolated Switching channels +/- 60V DC;
USB connection
Drive - NIDAQ951f1;
Programmable under MATLABTM
[6]
GPIB/USB adaptor
Agilent 82357B
Power Supply (used)
Computer (old)
AMD Athlon™ 64×2 Dual
[10]
Windows XP Professional Service Pack 3;
Chemstation vA.10.02 with OI Library Suite 15;
NI-DAQ drive;
MATLABTMLibrary;
Microsoft ExcelTM
Table 1: Equipment and their features used in this project.
equipment must be reliable, readily available; easy to operate, of
minimum capital and operational cost. For the sake of developing and
testing, on one hand, it should be operated as a stand-alone instrument;
on the other hand, it should be computer controllable for continuous
analysis.
HP 5890 II GC - retired but in good working condition
The gas chromatograph is the centerpiece of equipment for this
project. It is the most complicated and expensive component. Once the
decision on the selection of the GC is made, the other equipment to be
selected must be compatible with the GC. HP (now AgilentTM) GC has
a good reputation for its reliability. In our laboratory, and probably in
every other organic laboratory in North America, it is the most widely
used GC instrument of choice. It is often the case multiple units of these
GCs in good working condition are kicking around in the lab. The HP
5890 series is very common and is likely readily available. The HP5890
II (or HP5890 II Plus) was chosen over the model HP5890 due to its
computer controlling ability. Configuration of the GC is listed in Table
1. Detailed specifications can be found in its user’s manual [4].
TekmarTM LSC 3100 Purge-and-Trap - retired but in good
working condition
There are many brands of P&T devices on the market, while one
of the most often used is from TekmarTM. The obsolete LSC 3100 was
chosen over newer versions such as Tekmar’s Velocity or Stratum
models mainly due to this P&T’s stand-alone capabilities. We were
fortunate to have a retired unit in our lab that was still in good working
condition. The description and features of this instrument can be found
in the user’s manual [5].
Auto-sampler - built in-house
TekmarTM LSC 3100 P&T is a consecutive sample processor. In
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
another words, the sample cannot be continuously introduced into the
system. To put this device on-line, an auto-sampler has to be put in
front of it. To monitor the quality of raw and processed water, and the
effectiveness of individual stage of treatment process, more than one
stream often needs to be monitored. This can be done by having one
on-line system for each individual stream, or better having multiple
streams feed into one shared instrument. In order to save money for
this project the second approach of having two streams share the one
instrument was employed. For a water treatment plant, the source water
often varies with the change of seasons, especially during the spring
run-off period. Sediment, color, turbidity, dissolved and suspended
material change significantly throughout the year. The sample intake
can become clogged very quickly by sediments in raw water of poor
quality. For an on-line system to work properly, the sample, especially
the raw water sample, has to be filtered before being introduced into the
analytical system.
It is hard to find a commercial auto-sampler directly coupled
to the P&T without modification. Also, the commercially available
auto-samplers usually do not have stream selecting function and solid
removing capability. Thus, we decided to build our own auto-sampler
in-house. The detailed design and construction of this device are
described in the following sections.
Data and controller system
To make the system run automatically, the following hardware and
software is necessary: Hardware: A PC with USB ports; an AgilentTM
GPIB/USB 82357B [6] Interface; a National InstrumentsTM DAQ USB
6525.Software: WindowsTM XP Professional Service Pack 3 (or higher);
AgilentTM Chemstation ver A 10.02 (or higher) with OI Library Suite
15.0; a valve control drive (programmed in-house).
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 3 of 8
Filter
Screen
Filter house
Fix-volume
tubing
Measuring
unit house
Stream out
Stream in
Filtered
Sample
Over flow
(b)
(a)
Figure 2: Filter (a) and sample volume measuring unit (b).
Screen
filter
Fix-volume
tubing
M1
com
Drain
Stream 1
com
M2
3Way
3
1
Drain
com
com
1
3
V1
2
2
V3
V4
2W-NC
Drain
Sparger
Stream 2
V5
simple T
This Filter Unit (Figure 2a) consists of three pieces of tubing, a filter
screen and filter housing. Streaming water initially flows to the filter
housing unit through the “stream in” tubing. A small portion of this
stream passes through the filter screen with the sediments removed.
The removed sediment is carried out by the excess stream. The excess
stream do not pass through the filter screen; but instead exits the filter
housing through the “stream out” tubing (Figure 2a). The cleaner water
from within the filter screen cavity flows through the “filtered” tubing
towards the sample holder in the Sample Volume Measuring Unit
(Figure 2b).
The Sample Volume Measuring Unit (Figure 2b) is also constructed
in house. It consists of a sample housing, a bottomless cylinder (as the
holder) and connection tubing. At any given time, other than filling the
sparger on P&T, the sample in the “holder” is always at an over flowing
status, and thus the retained sample is always fresh with a fixed volume.
This volume of sample will be unloaded into the P&T sparger at each
sampling time.
Stream selection mechanisms: TekmarTM LSC 3100 can only
process one sample a time. Continuous feed of the water to the P&T
will make the purge process impossible. Solenoid valves were selected
to control the stream flow and consecutively feed the P&T LSC 3100.
There is no sample pump considered in the design, since in our plants,
the water streams are regulated to a relatively high pressure of 30 ~ 60
psi, which is high enough to push the water through the solenoid and
connecting tubing.
Referring to Figure 3, this simplified auto-sampler (without an
internal standard addition) consists of three solenoid valves (V1, V3,
V4), two manual mode-selection valves (M1, M2), the on-line filter,
sample measuring unit and the connection tubing. All the solenoid
valves are electronically operated. When the right voltage is applied to a
valve, the valve will be energized and turned ON (i.e., changed from its
normal status). To turn the valve off (back its normal status), the voltage
has to be removed from that valve.
All these valves and tubing are mounted on one piece of ¼ inch thick
aluminum board. The connections between the valves are illustrated in
Figure 3. This module can be operated in two different modes –either
with or without filtration. The sample size can be determined by the
sparger size or by sample holder size in the sample measuring unit
described above.
The valve operational sequences are described as follows:
• Stream 1 with filtration (default sequence S1)
Figure 3: The simplified auto-sampler (without an internal standard addition).
Accessories
Additional accessories are also required: DC power supply; custombuilt Tester/Initiator; manual valves; connection tubing; wires.
Construction of the System
Building the auto-sampler
Filter and sample volume measuring unit: Raw water samples
often contain large amounts of sediment which will quickly clog the
system unless the majority of the sediment is removed. A mechanism to
remove the sediment must be incorporated at the beginning of the run.
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Manual valve M1 to Left (L position, water flows up into the filter),
manual valve M2 to Right (R position, water from filter flows into this
valve and passes to the first 3-way solenoid V1); V1 programmed OFF
(sample flows through port 3 and 1 to the second 3-way solenoid V3).
V3 programmed OFF (water flows through the sample holder, the
overflow is discharged). By now, the sample is uploaded into the sample
holder. A signal is sent when the P&T is ready, switching both the 2-way
solenoid V4 ON (for releasing pressure) and the 3-way solenoid V3 ON
(blocking water from V1) and unloads the sample from the holder into
the sparger. When the sample unloading is complete, both V3 and V4
solenoids switch OFF automatically. The sample is ready to be purged.
• Stream1 without filtration (the only differences from the default
sequence S1 are the manual valves positioning, as shown in the
diagram above)
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 4 of 8
has more than enough power to energize all three solenoid valves and
leave enough room for future expansion (i.e., can add up to two more
valves if internal standard is needed).
USB-6525
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16
For e x p a n s i o n
Return Singnal
V1
V3
V4
Ground
Power Supply
+24VDC
Figure 4: Electrical connection between the solenoid valves and the power
supply via the NI DAQ.
Manual valve M1 to Right (R position, water flows down to M2),
manual valve M2 to Left (L position, water flows from M1 directly into
this valve and passes to the first 3-way solenoid V1); V1 programmed
OFF (water flows through port 3 and 1 to the second 3-way solenoid
V3). V3 programmed OFF (water flows through the sample holder). The
overflow is discharged. By now, the sample is uploaded into the sample
holder. A signal is sent when the P&T is ready, switching both the 2-way
solenoid V4 ON (for releasing pressure) and the 3-way solenoid V3 ON
(blocking water from V1) and unloads the sample from the holder into
the sparger. When the sample unloading is complete, both V3 and V4
solenoids switch OFF automatically. The sample is ready to be purged.
• Stream 2 (default sequence S2; Stream 2 cannot be filtered)
Manual valve M1 to Left (L position, stream1 flows up into the
filter), manual valve M2 to Right (R position, Stream1 from filter get
into this valve and pass to the first 3-way solenoid V1; V1 programmed
ON (Stream1 blocked here by Port 3 and flows through the filter drain).
Stream 2 flows through V1 from Port 2 to Port 1 and reaches V3, the
second 3-way solenoid). V3 V1 programmed OFF (water flows through
the sample holder, the overflow is discharged). By now, the sample is
uploaded into the sample holder.A signal is sent when the P&T is ready,
switching both the 2-way solenoid V4 ON (for releasing pressure) and
the 3-way solenoid V3 ON (blocking water from V1) and unloads the
sample from the holder into the sparger. When the unloaded sample
is complete, both V3 and V4 solenoids switch OFF automatically. The
sample is ready to be purged. V1 programmed OFF (allows Stream 1 to
pass through the sampling holder to the Drain).
Power supply: A used power supply (MW S-150-24) harvested
from an old TOC analyzer was used to energize the solenoids. The
specification of this power supply is listed in Table 1. This power supply
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Programmable switches: To make a solenoid valve change its status
at a scheduled time, there must be a switch to control the power to turn
the valve on or off. This switch has to be programmable either through
its own logic or through a computer. To control all the solenoid valves,
a set of programmable switches have to be used. After the consideration
of the convenience, programmability, function and price, a NI-DAQ
USB-6525 [6] was selected (purchased new). Its features are listed in
Table 1.
Connections: The electrical connection between the solenoid valves
and the power supply via the NI DAQ-6525 is illustrated in Figure 4
[7-9]. The NI DAQ-USB-6525 is computer controlled through an USB
connection, by a home developed program under MATLABTM [10]. The
program is compiled and can be run under MATLABTM Library. After
the control program of NI DAQ initialized, the designated channel of
the DAQ will be opened by closing the circuit at a pre-set time for a preset length of period. In this period of time, a voltage of +24V is applied
to the solenoid valve connected to this channel. This solenoid valve
will be turned on and changed from its normal status. At the end of
this period, the channel circuit is opened; the voltage is removed from
this valve; and the valve return to its normal status. The water stream is
controlled in this way.
Up to this point, the construction of the auto-sampler is finished.
The operation and timed events of the auto-sampler are described in
detail in the following section
Establish computer control of HP GC 5890 II
The HP 5890 II was used as a computer controlled instrument
before it was retired. The interface was a GPIB board with Windows TM
NT and an old version of Chemstation. However, the computer is too
out-of-date to accommodate the newly developed software. Further,
WindowsTM NT cannot handle USB adaptors, which is most often used
for connecting external devices at this time. Thus a newer computer was
selected. For the majority of new computers, there is no built- in slot
to accommodate a GPIB board. In order to establish communication
between the computer and the GC, the GPIB interface in the GC has
to be converted to a USB adaptor. The Agilent 82357B USB/GPIB
adaptor is designed for this purpose. Fortunately, we had one of these
devices already available in our lab. For this device to be functional,
Agilent’s OI Library Suite 15 (or higher), with ChemStation A10.02
(or higher) is needed. This software, in turn, needs the WindowsMT
XP Professional Service Pack 3 (or higher) operating system. Finally, a
suitable used computer system was selected with the features satisfying
these requirements (Table 1). The only physical connection between the
GC and the computer is between the GPIB interface on the GC and
the USB port on the computer through the 82357B USB/GPIB adaptor.
Configuration and settings of the software will not be provided in detail
here.
Establish communication between HP GC 5890 II and P&T
Tekmar LSC 3100
The goal of the setup is to synchronize the operation between
these two pieces of equipment. Two key requirements have to be met
– First, when the GC is not idle and at Ready Status, the P&T device
should not desorb the compounds it collected. The releasing of the
compounds should only happen when the GC is at a Ready Status.
The GC temperature program can be started in two ways – by software
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 5 of 8
GRND
Not ready
Ready
2
4
6
8
10
12
GC 5890 II
connector P6
1
Start
IN
3
5
7
Ready
Out
9
11
Ready
Out
LCS 3100
13 12 11 10 9 8 7 6 5 4
3
2 1
25 24 23 22 2120 19 18 17 16 15 14
Figure 5: Electrical connection between the GC and P/T.
32 31 30 29 28 27 26 25 2 4 23 22 21 20 19 18 17
9V
push botton
Purge-and-Trap
13 12 11 10 9 8 7 6 5 4
3
2 1
From Tekmar 3100
or other devices
25 24 23 22 2120 19 18 17 16 15 14
Figure 6: Trigger signal sent out by P&T to the computer to start the solenoid
valves controlling program via the NI DAQ USB-6525.
control (a mouse click on the start button) or by hardware (remote start
from an external signal). For continuous operation, the first approach
was ruled out, since one cannot click on the start button for each and
every sample. It has to be triggered by an external signal. Additionally,
the run has to be started at the time-point at which the compounds are
injected into the GC, i.e., when the P&T starts desorbing. The second
requirement is that the P&T must be at Ready Status when the autosampler starts taking the next sample. The auto-sampler needs a Ready
Signal from the P&T to start its procedure. Therefore, establishing
communication between the P&T and the GC, plus between the P&T
and the auto-sampler is essential.
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Since the starting point of P&T is independent of the GC, while
the GC starting is triggered by the P&T, the P&T can act as a control
point. Simply let the P&T run its procedures independently except for
the desorbing procedure (including the preheating). When the P&T
completes its purging procedure, it waits for a Ready signal from the
GC to desorb and start the GC analysis. When the P&T recover itself, it
sends a Ready Signal to the auto-sampler at a predetermined time point.
Thus, the P&T needs to obtain two commands - (1) a start command to
process a loaded sample from anywhere (GC, computer etc.), and (2) a
ready signal from the GC to begin desorbing.
Establish connection between the auto-sampler and the Purge
and Trap
Only the water lines need to be connected between the outlet of
the auto-sampler and the inlet of the P&T sparger. No direct electrical
connection between these two devices is needed. Signal transfer
is established through communication between the P&T and the
computer vial DAQ USB-6525. The connections between the P&T
and the DAQ-6525 are shown in Figure 6. When the GC is ready in
this configuration, it sends the ready signal to P&T, and the later starts
desorbing and sending a signal to the computer via the NI DAQ. A time
delay has to be programmed in the auto-sampler control to leave time
for the P&T to desorb and recover itself before preparing for the next
sample.
USB-6525
LCS 3100
The GC itself has a remote-start function. Specially configured
connection cables are available through Agilent or other suppliers.
Hand shaking between the GC and the P&T are established by an
electrical connection through a Tekmar cable (part number 14-6689186), which connects the GC end to RS-232-c, 25-pin, and to the
P&T end, 9-pin. Another Tekmar cable, part number 14-2991-000,
connected to the communication port (P/T end, 25-pin,) and the GC
(12-pinremote connection) to issue and receive Ready/Start signals.
The pin configuration and interconnections are illustrated in Figure 5.
With the correct user setting, upon completion of the purging process,
the P&T will wait for a ready signal. When the GC is ready, pins 5 and
9 will close briefly which momentarily short pins 3 and 4 in the P&T
communication port, starting the desorbing process.
Establish connection between the Auto-sampler and the HP
GC 5890 II
There is no water connection between the auto-sampler and the HP
GC 5890 II. The only possible electrical connection is between the GC
and the DAQ-6525 (as an option, not used at this time) is similar to that
shown in Figure 6, with the Ready signal from the GC to replace the
desorb signal from the P&T.
By now, the construction is finished. The overall diagram is shown
in Figure 7 as block pictures.
Overall Control and Data Handling
The remaining and the most difficult part of the project is the
automation of the system.
Individually, every module has been tested and works well. The
next step is to make them work together. The overall goal is to have
the system continuously sample from the water line, concentrate,
analyze and save/display the data. It also requires the system handles
two streams (A and B) alternatively. The entire process is explained as
the following:
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 6 of 8
Self
washing
filter
Valve panel
HP GC
5890II
Tekmar 3100
1
GPIB/USB
converter
2
Stream
NI DAQ
Water flow
Gas flow
Control and data PC
Figure 7: Block photo-diagram showing the connections of the overall system.
Detailed sequence
After all modules are initialized and synchronized after powering
on, both GC and P&T are at Ready Status. The following procedure
takes over and runs continuously (Figure 8) until it is interrupted
externally:
1. Start – Auto-sampler control program receives a start signal.
This can be from the push button in Figure 6, or from a pre-run
of the P&T.
2. Auto-sampler takes sample A and loads the sample to the P&T
sparger;
3. The P&T concentrates the sample (~ 15 minutes) and waits for
the HP GC to be ready (if it is not);
4. The P&T receives the ready signal from GC and transfers the
concentrated sample to GC and starts the GC run (the transfer
take 4 minutes and the GC run last 25-30 minutes, depends on
the column and the temperature program), at the same time
a signal is sent to the computer vial NI DAQ to start the time
delay before taking the next sample (The time delay should be
long enough to let the P&T fully recover);
5. The P&T recovers after transferring the sample to the GC (~ 15
minutes. Ensure the P&T is recovered before the GC run ends);
6. When the P&T has recovered, the auto-sampler starts taking
sample B and carries out the concentration procedure. (If the
concentration procedure completes before the GC is ready, it
will wait.)
7. When the GC run is finished, it saves the data file on the
hard drive in folder A. The file should contain the following
information: Run date and time, sample line A or B, the
concentration of the measured compounds.
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
8. The GC recovers. After the GC recovered and ready, it sends a
ready signal to the P&T. The same procedure as with line A is
carried out on line B. The data file has a different sample name
and stored in the folder B.
9. Steps 1 through 8 repeat themselves.
Computer controlling
Depending on the requirement of the sample lines, there are two
ways to automatically carry out the above sequences continuously.
Since both the MATLABTM program and ChemStation can access
other Windows applications through user defined macro program, this
provides a channel to exchange data between the GC, ChemStation,
and the MATLABTM software. One can build an ExcelTM file which
can be accessed by both software programs. The file contains the time
interval for the valve operation, sample name and other identification,
time stamp of the analysis, file name and path of the acquired data etc.
Both MATLABTM program and ChemStation read and write data from/
into this file to alter their variables in a predefined manner. Thus the
entire system is under complete computer control. The triggering signal
from the P&T to start the sampling will not be necessary. Due to the
limitation of this paper, detailed programming cannot be given here.
Interested readers can contact the author to discuss in more detail.
If only one stream of sample to be analyzed, the stream selection
function is not needed. The P&T can run continuously at a schedule
mode when the scheduled sequence is started. Thus, one can let the
P&T run independently and let the GC and auto-sampler run following
the trigger from the P&T. ChemStation can save the file when the GC
analysis complete. The file number will be automatically increase by 1
for the next sample. However, due to the stream selection function, this
is not used in this mode, and all the data will be stored in one folder.
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 7 of 8
Streams
A
Start
B
Sample
Manifold
trigger
Computer
A
Tekmar
3100
hand shake
B
Data file
HP GC
5890 II
Interruptor
End
Figure 8: Block diagram showing the operation of the on-line GC system. The steps in the green loop repeat after the START command is activated until the END
command is received. FID1 A (TEST -5890\SIG10037.D)
(a)
counts
Chromoform
90
80
7.157
1.960
2.558
60
1.593
70
50
0
5
10
15
20
25
min
25
min
FID1 A (TEST -5890\SIG10012.D)
counts
Chromoform
(b)
100
90
80
7.168
60
1.601
70
50
0
5
10
15
20
Figure 9: Chromatograms obtained by on-line measurement (a) and manual injection (b).
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Special Issue 12 • 2014
Citation: Zhao YH (2014) Development of an On-line GC System using Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Page 8 of 8
50 ppb
2.0 ppb
Compound
Average
Stdev
Average
Stdev
1,1 - dichloroethylene
49.08
2.19
1.70
0.18
MDL
0.54
methylene chloride
51.28
0.49
1.93
0.10
0.30
trans - 1,2 - dichloroethylene
53.54
1.58
1.86
0.15
0.45
cis - 1,2 - dichloroethylene
52.59
0.98
1.91
0.17
0.51
chloroform
49.19
0.82
1.93
0.11
0.34
1,1,1 - trichloroethane
49.23
1.78
1.73
0.19
0.58
carbon tetrachloride
48.03
2.46
1.53
0.30
0.91
benzene
62.22
1.28
2.19
0.15
0.46
trichloroethylene
52.61
1.29
1.87
0.16
0.47
1,2 - dichloropropane
49.39
0.73
1.77
0.10
0.30
bromodichloromethane
51.51
0.67
1.82
0.10
0.29
toluene
50.62
1.17
1.71
0.13
0.38
tetrachloroethylene
54.89
1.69
1.88
0.16
0.47
dibromochloromethane
83.40
0.75
2.94
0.14
0.43
chlorobenzene
49.94
0.74
1.71
0.13
0.38
ethylbenzene
51.51
1.23
1.73
0.14
0.42
1,4 - xylene
52.50
1.18
1.73
0.13
0.40
1,2 - xylene
56.26
1.67
3.83
0.25
0.75
bromoform
52.97
0.77
1.92
0.19
0.56
1,1,2,2 - tetrachloroethane
55.29
0.57
2.04
0.11
0.34
1,3 - dichlorobenzene
53.91
0.45
1.90
0.12
0.37
1,4 - dichlorobenzene
58.12
0.45
2.03
0.13
0.40
1,2 - dichlorobenzene
54.88
0.52
1.96
0.13
0.40
1,2,4 - trichlorobenzene
62.31
0.53
2.16
0.14
0.43
Manual
chloroform
One day -on-line
1 measurement
Average of 10
Stdev
22.81 ppb
19.05ppb
1.18ppb
Note: Repeated (10 times) analysis of solutions containing 50 ppb each compounds and 2 ppb each compound done manually after manual calibration. MDL is as 3 times
of standard deviation of the 2 ppb solution measurement.
Table 2: Performance data of the system.
Analytical Performance
Acknowledgement
Since no modification done on either the P&T or GC-FID, the
function and the measuring capabilities of these two instruments
remained the same with or without the connection of the autosampler.The sensitivity and detection limit should be the same with
manual sample introduction and auto-sampler introduction, as long
as the auto-sampler introduction is consistent. Further, auto-sampler
introduction needs pressurized sample reservoir and large quantity of
samples. It is not economically feasible to do auto-sampler introduction
calibration. Thus, the system was calibrated off-line by injecting the
calculated amount of calibration standard directly into the sparger.
After calibration, the system was then in conjunction with the autosampler.Calibration curve can be adjusted based on this comparison
if necessary. Figure 9 is a comparison of chromatograms obtained
from manual injection and from on-line measurement of the same
reservoir stream. The validation of the system is obvious. Table 2
listed the performance data for the system when it was run off-line.
Also, a comparison between the results obtained from the same stream
measured by manual injection and by auto-sampler introduction was
also listed in the table.
The author thanks Dr. Chuhong Fei, from AUG Signals Inc., for the assistance
in developing the solenoid control.
References
1. Environmental and Workplace Health (2012) Guidelines for Canadian Drinking
Water Quality. Health Canada.
2. Hammer MJ (1975) Water and Waste-water Technology. 4th edition, Technology
& Engineering. Wiley, USA.
3. Eaton AD, Franson MAH (2005) Standard Methods for the examination of water
and wastewater. 21st Edition, American Public Health Association, USA.
4. HP 5890 Series II and HP 5890 Series II Plus. Reference Manual.
5. Tekmar 3100 manual.pdf
6. NI USB-6525. National Instruments.
7. http://wattsupply.com/?gclid=COOi85LK8boCFSJlMgodMREA8g
8. 3 Way Solenoid Valves 8320 Series. ASCO.
9. 2 Way Solenoid Valves. ASCO.
10.82357B USB/GPIB Interface High-Speed USB 2.0. Agilent Technologies.
Summary
A functional On-Line GC system was developed using retired
existing equipment. Due to the easy availability of these devices in most
of the labs, this system can be built by any lab which has an interest in
its application. With a small investment, new and simplified devices can
be used to replace these old devices and make the system more compact
and reliable.
J Anal Bioanal Tech
ISSN:2155-9872 JABT, an open access journal
Citation: Zhao YH (2014) Development of an On-line GC System using
Existing Retired Equipment. J Anal Bioanal Tech S12: 008. doi:10.4172/21559872.S12-008
Special Issue 12 • 2014
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