PN 830-0120

PN 830-0120
11. Run test mix
Temperature limits
Columns have both lower and upper temperature limits. Lower limits
usually are at a phase change. Operation below this limit gives poor
separation and peak shape problems, but will not damage the column.
Inject a test mixture to further measure
system performance. The column test
mixture used by Agilent to determine
column quality is recommended. The
Performance Summary Chromatogram
included with each column can be
easily duplicated if the same conditions
and test mixture are used. Failure
to duplicate the chromatogram for a new column indicates an
installation, operation, or instrument problem. The problem must be
corrected before proceeding with sample analysis.
Two upper limits are often given. The lower is the isothermal limit; the
column can be held at this temperature for a prolonged time without
harm. The higher one is a programming limit. The column can be
heated to this limit for a short time (< 10 minutes).
Heating the column above the upper limits will significantly reduce
column life. Set the GC oven maximum temperature at or below the
column limit.
The story behind Agilent J&W advanced GC columns
12. Column use considerations
In 2000, Agilent, the inventor of fused silica GC tubing, acquired J&W
Scientific, the creator of the first GC stationary phase made from
cross-linked siloxane polymers. This partnership united the renowned
DB and HP column families, creating Agilent J&W GC Columns. The
innovative products that would follow include the Agilent J&W Ultra
Inert, High Efficiency, LTM, and PAH GC columns. In 2010, Agilent
acquired Varian, adding PLOT, Select, VF and CP-Sil to the most
extensive and innovative GC column offering in the industry.
For maximum operating life, keep the column temperature below
100 °C when a column is installed but is not in use for analysis.
Column storage
Seal the column ends with GC septa and return to the original box.
Upon reinstallation, cut column ends to insure that no small pieces
of septum have been left in the column.
Chemical compatibility
Bonded and cross-linked stationary phases are not damaged by
water or organic solvent injection. Inorganic acids (HCl, H2SO4,
H3PO4, HNO3, etc.) and bases (KOH, NaOH, etc.) should not be
injected into capillary columns. Rapid damage to the stationary phase
will occur. If chemical damage does occur, removing the front ½ to
1 meter of the column will often restore column performance.
The best low-bleed columns for sensitivity and
performance
Column bleed can decrease spectral integrity, reduce uptime, and
shorten column life. But Agilent J&W columns have the widest range of
low-bleed and standard stationary phases featuring superior inertness
and high upper temperature limits – especially for MS users performing
trace level analyses.
Rinsing columns
Do not solvent rinse the following non-bonded columns:
DX-1, DX-4, SE-30, SE-54, Carbowax 20M, Cyclodex-B, CycloSil-B,
HP-20M, HP-88 and CAM, HP-101, HP-17, HP-Chiral ß, CP-Sil 88,
Select Silanes. CP Volamine, CP-TCEP, CP-Cyclodextrin, and
CP-Chirasil Val.
Better precision for better results
Agilent J&W columns adhere to tight retention factor (k)
specifications, promoting consistent retention and separation.
They also feature narrow retention indexes and a high number of
theoretical plates per meter, ensuring narrow peaks and improving
the resolution of closely eluting peaks.
All other Agilent J&W standard and cross-linked WCOT columns are
solvent rinseable.
The industry’s tightest quality control specifications
Agilent’s stringent testing ensures reliable qualitative and
quantitative results – even for your most challenging compounds. For
example, we measure peak height ratios for both acids and bases to
ensure top performance for the widest range of compounds. We also
monitor peak symmetry and tailing for a broad scope of chemically
active compounds.
Retention gaps
The stationary phase of non-bonded columns is easily disrupted
during the injection process. Attach a 3 to 5 meter retention gap
to the front of the column. This minimizes the amount of stationary
phase damage, especially with on-column and splitless inlets.
5
As the world’s leading provider of GC capillary columns, Agilent is
uniquely positioned to offer you superior quality and unmatched
service and support.
For additional column recommendations, chromatograms, and method
parameters, go to www.agilent.com/chem/myGCcolumns
They may be small... but Agilent inlet supplies can
have a big impact on your results
Agilent inlet supplies are engineered with the same reliability you
expect from Agilent instruments. And they are designed to work
with your new Agilent GC or GC/MS system. What’s more, Agilent
supplies are designed for fast, easy replacement, so you can get your
system running again quickly.
Be sure to stock up on these essentials now – so they will always be
there when you need them:
• Premium non-stick inlet septa and non-stick liner O-ring
(5188-5365)
• Certified vials, caps and septa
• Ultra Inert injection port liners
• Pre-conditioned ferrules in ultra-clean packaging
• Metal injection-molded inlet Gold Seals (5188-5367)
• Gold standard autosampler syringes
Learn more
www.agilent.com/chem
AGILENT J&W CAPILLARY GC COLUMN
INSTALLATION GUIDE
Buy online
www.agilent.com/chem/store
Find an Agilent Representative or
Agilent Authorized Distributor
www.agilent.com/chem/contactus
U.S. and Canada
1-800-227-9770, [email protected]
Europe
[email protected]
Asia Pacific
[email protected]
India
india_lsca_marke[email protected]
Agilent shall not be liable for errors contained herein or for incidental
or consequential damages in connection with the furnishing,
performance, or use of this material.
Information, descriptions, and specifications in this publication
are subject to change without notice.
© Agilent Technologies, Inc., 2013
Published in the USA, January 2, 2013
Publication Number 830-0120
These instructions are suitable for the
majority of the capillary columns that
Agilent J&W manufactures. There may
be more specific conditioning, care, and
maintenance procedures for your new
GC column (e.g., PLOT columns).
Be certain to read all the information that comes with your new GC
column to ensure that the column performs to expectations.
A fused silica capillary GC column (Figure 1) consists of:
• An amber-brown polyimide exterior coating that protects the
tubing from breakage.
• The fused silica tubing.
• A stationary phase that is evenly coated onto the inner wall
of the tubing. Common phases are silicon-based polymers
(polysiloxanes), polyethylene glycols, and solid adsorbents.
Maximize capillary GC column performance and lifetime by
following these recommended guidelines for proper installation.
Polyimide coating
Fused silica
Stationary phase
Figure 1. Capillary column
Tools for capillary column installation
Column cutting tool such as a diamond-, carbide-, or sapphire-tipped
pencil, or a ceramic cleaving wedge
Supply of an appropriate nonretained compound
Column test mixture (optional)
Electronic flowmeter (optional)
Electronic leak detector (optional)
1. Check traps, carrier gas, septum, and liner
Check gas purifiers for expiration and replace if necessary. Install
a new septum in the inlet. If needed, clean or replace the inlet
liner and gold-plated inlet seal, especially after injecting dirty
samples or when analyzing active compounds. The liquid phase in
the column is easily damaged by oxygen at temperatures above
ambient. Use purifiers on the carrier gas lines to extend column
lifetime and minimize background noise. An indicating filter that
removes oxygen, moisture, and hydrocarbons such as the Agilent
Gas Clean GC/MS filter is highly recommended for the carrier gas.
The optimal insertion distance of the column into the inlet depends
on the inlet type. Consult the GC instruction manual for the proper
insertion depth and technique.
The Agilent Gas Clean filters can also be added to detectors gas lines to
improve sensitivity and lifetime.
2. Place nut and ferrule on the column, carefully cut
column end
With the column at its proper position, finger-tighten the column
nut. Use a wrench to tighten an additional ½ turn. If the column can
be moved in the fitting, tighten another ¼ turn. Failure to achieve a
leak-free seal will cause rapid and permanent column damage. Do
not move the column while tightening the nut.
Warning: Be careful! The oven and/or inlet may be hot enough to
cause burns. If the inlet is hot, wear heat-resistent gloves to protect
your hands.
Ferrules, especially those made of graphite/Vespel, will change
shape slightly upon heating. If the column was installed while the
inlet and detector were cool, retighten the fitting. It is also good
practice to make sure the column nuts are tight after conditioning
the column.
Warning: Wear safety glasses to protect your eyes from flying
particles while handling, cutting, or installing glass or fused silica
capillary columns. Use care in handling these columns to prevent
puncture wounds.
Place the column nut and ferrule over one end of the column. There
is no front or back of the column; however, the posts of the column
cage usually point towards the oven door.
4. Turn on carrier gas
Adjust the head pressure to obtain a reasonable flow rate of carrier
gas (Table 1). These values are recommended as starting points
only. The actual head pressure will depend on the carrier gas
velocity or flows set in Step 9.
Cut the end of the column after nut and ferrule placement. Hold the
section of column to be cut against a finger. In one motion, scribe
the outside of the column using a suitable cutting tool. Do not cut
completely through the tubing. Grasp the column on each side of the
scribe mark and bend away from the mark. Inspect the column end
with a magnifier. Ensure the cut is at a right angle to the tubing wall and
free of chips, burrs, or uneven areas (Figure 2). Recut if necessary.
length id (mm)
(m)
0.10
0.18
35-45
0.20
40
50
60
3. Install column into the inlet
105
Unwind enough column to obtain a smoothly curved section of
tubing connected to the inlet. Avoid tight bends as this stresses
the tubing and could cause breakage. Make sure that column tags,
sharp edges, or other items do not rub against the column.
5-10
1-2
20-30
15-25
10-20
3-5
2-4
6-10
4-8
8-14
5-10
35-50
30-60
15-25
30-45
75
Place the column on the GC oven column hanger. Make sure the
column tubing does not touch the sides of the oven.
0.53
75-100 10-20
30
Figure 2. Cutting a fused silica capillary column.
0.45
60-80
20-30
10-15
Table 1. Approximate column head pressure settings for He carrier gas (psig)
Compound
FID
Methane, butane
TCD
Methane, butane, argon, air
ECD
Methylene chloride , SF 6, CF2CL 2
NPD
Acetonitrile2,3
PID
Ethylene, acetylene
MS
Methane, butane, argon, air
2
Most of these compounds are significantly retained on PLOT columns.
Do not inject liquid. Use a very dilute headspace injection.
3
A cetonitrile is retained by most columns at temperatures below 100 °C.
Heat the column to 100 °C or higher to set linear velocity.
2
It is highly recommended to use gas purifiers such as the Agilent Gas
Clean filter system, to ensure the highest quality gas while keeping gas
lines clean and leak-free. Clean gases reduce risk of column damage,
sensitivity loss, and instrument downtime.
Table 2. Nonretained compounds1
Procedure
With the column temperature at 35 to 40 °C, rapidly inject 1 to 2 µL of a
nonretained compound with the split/splitless inlet in the split mode. If
using Megabore direct or cool on-column modes, dilute the nonretained
compound so that the sample will not saturate the detector.
Warning: Hydrogen forms explosive mixtures with air at concentrations
of 4 to 10% hydrogen. Its high diffusivity minimizes this possibility, but
the danger should not be discounted.
A very sharp and symmetrical peak should be obtained (Figure 3); a
small amount of peak tailing may be observed with splitless injection.
If no peak appears, there may not be any carrier gas flow. Check the
regulators, gas supply and flow controllers for the proper settings. Make
sure that the detector, recorder, and syringe are functioning properly.
If the nonretained compound is tailing, there may be a leak in the inlet,
poor column installation, or an excessively low split ratio. Reinstall the
column and check the inlet for leaks. A nontailing peak is required before
continuing.
Follow the installation precautions in Step 2 and 3 for the detector side
while installing the column into the detector. Confirm all detector gas
flows with an accurate flow-measuring device.
Inspect the GC system for leaks before heating the column for the first
time. An electronic leak detector is the most reliable way to check the
inlet and detector fittings. Do not use Snoop. If use of a liquid is desired,
try a 50/50 mixture of isopropanol/water.
equation. Adjust the column head pressure until the desired average
linear velocity is obtained.
Caution: Heating a column without carrier gas flow or while oxygen is
present in the carrier gas stream will rapidly and permanently damage
the column.
µ = L/tr
Purge the column with carrier gas for 15 minutes. Heat the column
to its upper temperature limit or a temperature 10 to 20 °C above the
highest operating temperature of the method, whichever is lower. Do
not exceed the column upper limit or column damage will result.
7. Confirm carrier gas flow and proper column
installation
Electronic pressure control (EPC) allows direct entry of carrier gas linear
velocity or flow rate. It is critical that correct column dimensions are entered
into the PC software or via the GC keypad for accurate velocity or flow
values to be set.
Always consult the column performance summary sheet that accompanies
the column for accurate inner diameter information.
Figure 3. Methane peaks
3
Where
µ = Average linear velocity (cm/sec)
L = Column length (cm)
tr = Retention time nonretained peak (sec)
Recommended average linear velocities
Helium:
30 to 40 cm/sec
Hydrogen:
50 to 80 cm/sec
After the column has reached the conditioning temperature, observe
the baseline. It will rise for 5 to 30 minutes, then drop for another 30
to 90 minutes. A flat baseline should be obtained 1 to 3 hours after
reaching the conditioning temperature. If the baseline does not stabilize
after 2 to 3 hours or does not remain constant, stop the conditioning
process.* An unstable baseline can be caused by a leak in the carrier
gas line or inlet area, or by system contamination. Fix either problem
before continuing.
GCs with EPC
The linear velocity can be entered into the PC software or the GC keypad
and remains constant. The correct column dimensions must be entered into
the PC software or the GC keypad for the system to accurately set the linear
velocity. Refer to the inner diameter of the column which is included on the
column performance summary sheet (this is a nominal value).
Polar stationary phases and thick films usually require longer times to
stabilize than nonpolar phases and thinner films. PLOT columns require
special conditioning procedures. Refer to the column information sheet
for the appropriate procedure.
10. Bleed test
After the column is conditioned, run a blank (no injection) chromatogram.
Start at 40 to 50 °C, ramp at 10 to 20 °C/min and hold for 10 to 15 minutes
at the conditioning temperature. Save this background trace for future
comparisons. See Figure 4.
Some detectors, such as ECDs and MSDs, may stabilize faster if the
column is not connected to the detector during column conditioning.
There should be no peaks in the blank chromatogram. Peaks indicate a
contamination problem, usually in the inlet area. As a column degrades
with normal usage, the magnitude of the baseline rise will increase. If the
baseline rise occurs at a much lower temperature than previously obtained,
the column and/or GC is most likely contaminated or damaged.
If the column is conditioned with the detector end disconnected, a
small portion of the column end may be damaged. Remove 10 to
20 cm of the exposed column end before connecting the column to
the detector.
* Thick-film and PLOT columns may take longer.
9. Accurately set the carrier gas velocity
Column
Agilent P/N
Carrier
Oven
Inlet
Detector
For capillary columns, the average linear velocity (µ) is a better and
more meaningful measure of the carrier gas than the volumetric flow
rate. The carrier gas linear velocity directly influences the retention
time and efficiency.
Confirm carrier gas flow as described in Step 4 or by injecting a nonretained
compound. Recommended nonretained compounds are in Table 2.
2
8. Condition the column
Detector
1
6. Inspect for leaks
8-12
25
Properly cut column
0.32
10-15
15
20
0.25
5-10
12
Improperly cut column
Carrier gas selection
High purity helium and hydrogen are the preferred carrier gases
for capillary columns; nitrogen is not recommended. Hydrogen is
recommended for use with microbore GC columns (0.10 mm id and
smaller). A gas purity of 99.995% or better is recommended with
oxygen being the most important impurity to avoid (less than
1 ppm oxygen).
5. Install the column into the detector
Column
10
Place the free end of the column in a small vial of hexane. A steady
stream of bubbles should be visible. If bubbles are not seen, check the
carrier gas supply, flow controllers, etc. for proper settings and for leaks.
Wipe off any residual solvent before continuing.
GCs without EPC
Carrier gas velocity changes with oven temperature as carrier gas
viscosity changes. Always set linear velocity at the same temperature
for a given analysis (often the initial oven temperature). Inject 1 to
2 µL of the appropriate nonretained compound and calculate the
linear velocity using the retention time of the peak and the following
DB-5, 30 m x 0.25 mm id, 0.25 µm
122-5032
Helium at 40 cm/sec
50 to 325 °C at 10 °C/min, 325 °C for 5 min
Split 1:100, 250 °C
FID, 300 °C, Nitrogen makeup gas at 30 mL/min
Figure 4. Bleed profile
4
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