ASTM E1510-95(2021)

Standard Practice for Installing Fused Silica Open Tubular Capillary Columns in Gas Chromatographs

SIGNIFICANCE AND USE
5.1 This practice is intended to be used by all analysts using fused silica capillary chromatography. It contains the recommended steps for installation, preparation, proper installation, and continued column maintenance.
SCOPE
1.1 This practice covers the installation and maintenance of fused silica capillary columns in gas chromatographs that are already retrofitted for their use. This practice excludes information on:  
1.1.1 Injection techniques.  
1.1.2 Column selection.  
1.1.3 Data acquisition.  
1.1.4 System troubleshooting and maintenance.  
1.2 For additional information on gas chromatography, please refer to Practice E260. For specific precautions, see 7.2.2.2(1), 7.2.2.2(2), 7.2.7, and 7.2.7.2.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific safety information, see Section 6, 7.2.2.2(1), 7.2.2.2(2), 7.2.7, and 7.2.7.2.2  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2021
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E13 - Molecular Spectroscopy and Separation Science
• Drafting Committee: E13.19 - Separation Science

Relations

• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM E260-96(2011) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM E355-96(2007) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Mar-2007
• Refers: ASTM E260-96(2006) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Mar-2006
• Refers: ASTM E355-96 - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96 - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E355-96(2001) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96(2001) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001

Overview

ASTM E1510-95(2021) is the internationally recognized standard practice for installing fused silica open tubular capillary columns in gas chromatographs. Developed by ASTM International, this standard is essential for laboratories and analysts conducting high-performance gas chromatography (GC) using fused silica capillary columns. The document provides comprehensive, step-by-step guidance for the preparation, installation, and ongoing maintenance of these columns. It is particularly relevant for gas chromatographs already adapted for capillary use, ensuring optimal system performance and reliable analytical results.

Key Topics

• Column Preparation & Handling: Recommends best practices for handling fused silica capillary columns, including inspection for damage, proper cutting techniques, and minimizing contamination.
• Installation Procedures: Outlines the necessary steps - such as preparing injector and detector zones, cleaning and deactivating sleeves, and setting carrier gases - to achieve correct and leak-free installation.
• Carrier Gas Selection: Highlights the importance of using high-purity gases (typically helium or hydrogen) and discusses their benefits and hazards, including efficiency considerations and explosion risk when using hydrogen.
• Connection & Fitting: Details the use of appropriate ferrules and nuts, emphasizing correct positioning and the importance of avoiding sharp bends and stress points on the column.
• Leak Detection & System Integrity: Describes reliable methods for ensuring gas-tight integrity throughout the system, with guidance on avoiding contaminant introduction from leak-checking agents.
• Column Maintenance: Covers routine maintenance steps, such as injector sleeve cleaning, septum replacement, and system calibration to extend column life and maintain performance.

Applications

ASTM E1510-95(2021) is vital in various practical scenarios, including:

• Analytical Chemistry Laboratories: Ensures accurate, reproducible results in environmental, pharmaceutical, petrochemical, and food safety testing.
• Quality Control: Provides a standardized approach to column installation and maintenance, minimizing variables and meeting regulatory requirements.
• Research & Development: Supports advanced separation science by establishing best practices when working with sensitive or challenging analytes.
• Instrument Operation & Training: Acts as a reference for laboratory personnel, new analysts, and training programs in chromatographic techniques.
• Maintenance Optimization: Reduces downtime and costly column failures by outlining effective preventative care strategies.

Related Standards

Adhering to ASTM E1510-95(2021) often requires referencing complementary standards and resources:

• ASTM E260 - Practice for Packed Column Gas Chromatography, which covers broader GC principles.
• ASTM E355 - Definitions and relationships of terms in gas chromatography.
• Compressed Gas Association (CGA) Guidelines - Safety and handling of gases (e.g., CGA P-1, G-5.4, P-9, V-7, HB-3).
• Other Instrument Manuals & Manufacturer Guidelines - For equipment-specific recommendations and safety information.

These standards collectively support researchers and technicians in aligning with best practices for safe, efficient, and reliable capillary column chromatography.

---

Keywords: ASTM E1510-95(2021), gas chromatography, fused silica capillary columns, column installation, analytical laboratory standards, column maintenance, carrier gases, hydrogen safety, chromatography best practices, laboratory safety, chromatograph setup, ASTM standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:E1510 −95 (Reapproved 2021)
Standard Practice for
Installing Fused Silica Open Tubular Capillary Columns in
Gas Chromatographs
This standard is issued under the fixed designation E1510; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This practice covers the installation and maintenance of
E260Practice for Packed Column Gas Chromatography
fused silica capillary columns in gas chromatographs that are
E355PracticeforGasChromatographyTermsandRelation-
already retrofitted for their use. This practice excludes infor-
ships
mation on:
2.2 CGA Publications:
1.1.1 Injection techniques.
CGAP-1SafeHandlingofCompressedGasesinContainers
1.1.2 Column selection.
CGA G-5.4Standard for Hydrogen Piping Systems at Con-
1.1.3 Data acquisition.
sumer Locations
1.1.4 System troubleshooting and maintenance.
CGA P-9The Inert Gases: Argon, Nitrogen and Helium
CGA V-7Standard Method of Determining Cylinder Valve
1.2 For additional information on gas chromatography,
Outlet Connections for Industrial Gas Mixtures
please refer to Practice E260. For specific precautions, see
CGA P-12Safe Handling of Cryogenic Liquids
7.2.2.2(1), 7.2.2.2(2), 7.2.7, and 7.2.7.2.
HB-3Handbook of Compressed Gases
1.3 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Terms and relations are defined in Practice E355.
1.4 This standard does not purport to address all of the
3.2 Nomenclature for open tubular or capillary columns
safety concerns, if any, associated with its use. It is the
with a bore of 0.75 mm or less:
responsibility of the user of this standard to establish appro-
3.3 porous layer open tubular (PLOT)—refers to columns
priate safety, health, and environmental practices and deter-
with particles attached on the inside wall consisting of copo-
mine the applicability of regulatory limitations prior to use.
lymers such as styrene/divinylbenzene, molecular sieves, or
For specific safety information, see Section 6, 7.2.2.2(1),
adsorbentssuchasAl O infilmthicknessesof5µmto50µm.
2 2 2
7.2.2.2(2), 7.2.7, and 7.2.7.2.
3.4 support coated open tubular (SCOT)—refers to fine
1.5 This international standard was developed in accor-
particles (silica or fine diatomite) coated with liquid stationary
dance with internationally recognized principles on standard-
phase, which is then deposited on the inside column wall to
ization established in the Decision on Principles for the
improve stationary phase stability and sample capacity.
Development of International Standards, Guides and Recom-
3.5 wall coated open tubular (WCOT)—refers to columns
mendations issued by the World Trade Organization Technical
coated on the inside wall with a liquid stationary phase in film
Barriers to Trade (TBT) Committee.
thicknesses of 0.1µm to 10.0 µm.Also referred to as FSOT or
fused silica open tubular.
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
mittee E13.19 on Separation Science. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2021. Published April 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 1993. Last previous edition approved in 2013 as E1510–95 (2013) . Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E1510-95R21. the ASTM website.
2 4
Reprinted by permission of Restek Corp., 110 Benner Circle, Bellefonte, PA Available from Compressed Gas Association (CGA), 8484 Westpark Drive,
16823-8812. Suite 220, McLean, VA 22102, http://www.cganet.com.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1510−95 (2021)
TABLE 1 Typical Splitter Vent Flow Rates (50 to 1 split ratio)
(at optimum linear velocity)
0.25 mm ID, 0.32 mm ID, 0.53 mm ID,
Carrier gas
3 3 3
cm /min cm /min cm /min
helium 35 80 125
hydrogen 70 160 250
Carrier gas: Hydrogen Carrier gas: Helium
Linear velocity: 40 cm/s Linear velocity: 20 cm/s
NOTE1—Fig.2showsthattheresolutionissimilarbuttheanalysistime
is reduced by 50% when comparing hydrogen to helium in an isothermal
analysis using optimum flow velocities.
NOTE 2—Hydrogen provides similar resolution in one-half the analysis
time of helium for an isothermal analysis.
NOTE1—Thecurvesweregeneratedbyplottingtheheightequivalentto
NOTE 3—
a theoretical plate (length of column divided by the total number of
1. Tetrachloro-m- 8. Heptachlor epoxide 15. Endosulfan II
theoretical plates, H.E.T.P.) against the column’s average linear velocity.
xylene 9. γ-chlordane 16. DDD
The lowest point on the curve indicates the carrier gas velocity in which
2. α-BHC 10. Endosulfan I 17. Endrin aldehyde
the highest column efficiency is reached.
3. β-BHC 11. α-chlordane 18. Endosulfan sulfate
NOTE 2—Gases information available from Compressed Gas Associa- 4. γ-BHC 12. Dieldrin 19. DDT
5. δ-BHC 13. DDE 20. Endrin ketone
tion (CGA), 8484 Westpark Drive, Suite 220, McLean, VA 22102,
6. Heptachlor 14. Endrin 21. Methyoxychlor
http://www.cganet.com.
7. Aldrin
FIG. 1Van Deemter Profile for Hydrogen, Helium, and Nitrogen
Carrier Gases
NOTE 4—30 m, 0.25mm ID, 0.25 µm 5% diphenyl−95% dimethyl
polysiloxane 0.1-µL split injection of chlorinated pesticides.
Oven temperature: 210°C isothermal
4. Summary of Practice
Injector and detector temperature: 250 °C ⁄300 °C
−11
4.1 The packed gas chromatography system is described in ECD sensitivity: 512 × 10
Split vent: 100 cm /min
Practice E260 and is essentially the same as a capillary gas
chromatographysystemexceptformodificationstotheinjector
FIG. 2Hydrogen Versus Helium (Isothermal Analysis)
and detector to accommodate the low flow rates and sample
capacity associated with capillary columns. Refer to the gas
chromatography(GC)instrumentmanualforspecificdetailson
injector or detector pneumatics for capillary columns.
4.2 Prior to performing a capillary GC analysis, the capil-
lary column configuration must be determined. The stationary
phase type, stationary phase film thickness, column inside
diameter, and column length must be selected. It is beyond the
FIG. 3Capping Silanol Groups with Dimethyl Dichlorosilane
scope of this practice to provide these details. Consult a (DMDCS)
column or instrument supplier for details on selecting the
appropriate capillary column configuration.
Association, a member group of specialty and bulk gas
4.3 Apply caution during handling or installation to avoid
suppliers, publishes the following guidelines to assist the
scratching or abrading the protective outer coating of the
laboratory chemist to establish a safe work environment: CGA
column. Scratches or abrasions cause the fused silica capillary
P-1, CGA G-5.4, CGA P-9, CGA V-7, CGA P-12, and HB-3.
column to spontaneously break or fail during usage.
7. Installation Procedure for Fused Silica Capillary
5. Significance and Use
Columns
5.1 Thispracticeisintendedtobeusedbyallanalystsusing
7.1 Abriefoutlineofthestepsnecessaryforinstallingfused
fused silica capillary chromatography. It contains the recom-
silica capillary columns in capillary dedicated gas chromato-
mended steps for installation, preparation, proper installation,
graphs is as follows:
and continued column maintenance.
7.1.1 Cool all heated zones and replace spent oxygen and
moisture scrubbers,
6. Hazards
7.1.2 Clean or deactivate, or both, injector and detector
6.1 Gas Handling Safety—The safe handling of compressed sleeves (if necessary),
gases and cryogenic liquids for use in chromatography is the 7.1.3 Replace critical injector and detector seals,
responsibility of every laboratory. The Compressed Gas 7.1.4 Replace septum,
E1510−95 (2021)
7.1.17 Set injector and detector temperatures and turn on
detector when temperatures have equilibrated (Warning—Do
not exceed the phase’s maximum operating temperature),
7.1.18 Inject a non-retained substance (usually methane) to
set the proper dead time (linear velocity),
7.1.19 Check system integrity by making sure dead volume
peak does not tail,
7.1.20 Condition the column at the maximum operating
temperature for 2 h (consult column manufacturer’s literature)
to stabilize the baseline,
7.1.21 Reinject a non-retained substance (usually methane)
to set the proper linear velocity,
7.1.22 Run test mixtures to confirm proper installation and
NOTE 1—Septum bleed can obscure or co-elute with compounds of
interest, thus decreasing the analytical accuracy. column performance, and
NOTE 2—
7.1.23 Calibrate instrument and inject samples.
1. 2,4,5,6-tetrachloro- 8. Heptachlor 16. p,p-DDD
7.2 The following section provides in-depth information on
m-xylene (IS) epoxide 17. Endrin aldehyde
instrument preparation procedures for installing and operating
2. α-BHC 9. γ-chlordane 18. Endosulfan sul-
3. β-BHC 10. Endosulfan I fate
fused silica capillary columns in capillary dedicated gas
4. γ-BHC 11. α-chlordane 19. p,p-DDT
chromatographs:
5. δ-BHC 12. Dieldrin 20. Endrin ketone
6. Heptachlor 13. p,p-DDE 21. Methyoxychlor 7.2.1 Gas Purification—The carrier gas must contain less
7. Aldrin 14. Endrin 22. Decachlorobi-
than 1 ppm of oxygen, moisture, or any other trace contami-
15. Endosulfan II phenyl (IS)
nants. Otherwise, oxygen and moisture degrade column
performance, decrease column lifetime, and increase back-
NOTE 3—30 m, 0.53mm ID, 0.50 µm 5% diphenyl−95% dimethyl
polysiloxane 0.1 µL direct injection of 50 pg pesticide standard.
ground stationary phase bleed. Contaminants such as trace
hydrocarbons cause ghost peaks to appear during temperature
Oven temperature: 150 °C to 275 °C at
4 °C ⁄min,
programming and degrade the validity of the analytical data.
hold15min
Make-up gas should also be contaminant-free or baseline
Injector temperature: 250 °C Detector temperature: 300 °C
Carrier gas: Helium fluctuations and excessive detector noise may occur. Detector
Linear velocity: 40 cm/s (Flow rate: 10 cm /min)
gases such as hydrogen and compressed air should be free of
−11
ECD sensitivity: 8 × 10 AFS
water and hydrocarbon or excessive baseline noise may occur.
FIG. 4ECD Septum Bleed 7.2.1.1 Install purifiers as closely as possible to the GC’s
bulkhead fitting, rather than system-wide. If purifiers are
installed system-wide, a leaky fitting downstream of the
purifier could allow oxygen and moisture to enter the gas
stream and degrade column performance.
7.1.5 Set make-up and detector gas flow rates,
7.2.1.2 Only high–purity gases should be used for capillary
7.1.6 Carefully inspect the column for damage or breakage,
chromatography.All regulators should be equipped with stain-
7.1.7 Cutapproximately10cmfromeachendofthecolumn
less steel diaphragms. Regulators equipped with rubber or
using a ceramic scoring wafer or sapphire scribe,
elastomeric diaphragms should not be used because oxygen,
7.1.8 Install nut and appropriately sized ferrule on both
moisture, and elastomeric contaminants migrate through the
column ends,
diaphragm and enter the flow.
7.1.9 Cut an additional 10 cm from each end of the column
to remove ferrule shards, 7.2.1.3 Both indicating and non-indicating traps are avail-
able from most capillary column suppliers. Indicating purifiers
7.1.10 Mount the capillary column in the oven using a
bracket to protect the column from becoming scratched or are recommended since they allow analysts to visually assess
whether the purifier has exceeded its useful life. Also, a
abraded and to prevent it from touching the oven wall,
7.1.11 Connect the column to the inlet at the appropriate moisture trap should be installed prior to the oxygen trap. If
hydrocarbon contamination is suspected, a hydrocarbon trap
distance as indicated in the instrument manual,
7.1.12 Set the approximate column flow rate by adjusting should be installed between the moisture and oxygen trap.
Sincemostindicatingtrapsaremadefromglass,careshouldbe
the head pressure (see column manufacturer’s literature),
7.1.13 Set split vent, septa purge, and any other applicable taken not to apply lateral torque on the fittings, or they will
snap. To prevent spontaneous breakage of the trap, the line
inlet gases according to the instrument specifications,
7.1.14 Confirmflowbyimmersingcolumnoutletinavialof leading to and from the purifier should be coiled to relieve
strain and isolate instrument vibrations.
acetone or methylene chloride,
7.1.15 Connectthecolumntothedetectorattheappropriate 7.2.2 Carrier Gas Selection—Afastcarriergasthatexhibits
distance as indicated in the instrument manual, a flat van Deemter profile is essential to obtain optimum
7.1.16 Check for leaks at the inlet or outlet using a thermal capillary column performance. Because capillary columns
conductivity leak detector (do not use soaps or liquid-based average30minlength(comparedto2mforpackedcolumns),
leak detectors), a carrier gas that minimizes the effect of dead time is
E1510−95 (2021)
important. In addition, capillary columns are usually head
pressure controlled (not flow controlled like most packed
columns), which cause the carrier gas flow rate to decrease by
40% when the column is programmed from ambient to
300°C.Therefore,acarriergasthatretainshighefficiencyover
a wide range of flow rates is essential towards obtaining good
resolution throughout a temperature–programmed chromato-
graphic analysis.
7.2.2.1 The optimum average linear gas velocity for hydro-
gen (u : 40 cm/s) is greater than all the others, and hydrogen
opt
exhibits the flattest van Deemter profile. Helium is the next
best choice (u : 20 cm/s). Note that head pressures at
opt
optimum flow rates are similar for hydrogen and helium
Carrier gas: Hydrogen Carrier gas: Helium
because hydrogen has half the viscosity but double the linear
Linear velocity: 40 cm/s Linear velocity: 20cm/s
velocityashelium.Becauseofthelowoptimumlinearvelocity
(u : 10 cm/s) and steep van Deemter profile, nitrogen gives NOTE1—Hydrogenisonlyslightlyfasterthanheliumwhenbothcarrier
opt
gases are operated under the same temperature-programmed oven condi-
inferior performance with capillary columns and is usually not
tions.
recommended.
NOTE 2—
7.2.2.2 Temperature programming usually provides similar
1. Phenol
analysis times between hydrogen and helium since the elution
2. 2-chlorophenol 7. 2,4,6-trichlorophenol
3. 2-nitrophenol 8. 2,4-dinitrophenol
ofmostcompoundsstronglydependsontheoventemperature.
4. 2,4-dimethyl phenol 9. 4-nitrophenol
Therefore, the savings in analysis times are not as great as
5. 2,4,dichlorophenol 10. 2-methyl-4,6-dinitrophenol
when isothermal oven conditions are utilized. In addition,
6. 4-chloro-3-methyl phenol 11. Pentachlorophenol
slower carrier gases, such as helium, can improve the separa-
NOTE 3—30 m, 0.25mm ID, 0.25 µm 5% diphenyl – 95% dimethyl
tion of very low boiling or early eluting compounds since they
polysiloxane 0.1-µL split injection of phenols.
allow more interaction with the stationary phase. Fig. 5
Oven temperature: 50 °C (hold 4 min) to 250 °C at 8 °C ⁄min (hold 5
illustrates that hydrogen is only slightly faster than helium
min)
when both carrier gases are operated under the same tempera-
Injector and detector temperature: 280 °C
–11
FID sensitivity: 32 × 10
ture to programmed conditions. Also, note that helium im-
Split vent: 40 cm /min
proves the resolution of the early eluting compounds (Peaks 1
and2)ascomparedtohydrogenforatemperatureprogrammed
FIG. 5Hydrogen Versus Helium (Temperature-Programmed Mode)
analysis.
(1) Warning—Exert caution when using hydrogen as a
carriergas.Hydrogenisexplosivewhenconcentrationsexceed
unlikely. However, a spark from static electricity (particularly
4% in air and should only be used by individuals who have
the case if a lab is carpeted) can ignite the hydrogen exiting
received proper training and understand the potential hazards.
from septum purge or split vent, which could cause a burn or
Proper safety precautions should be utilized to prevent an
a fire. Since hydrogen flames are colorless, an analyst would
explosion in the oven chamber. Some gas chromatographs are
notknowthatthesplitventwasignitedunlessheinadvertently
designed with spring–loaded doors, perforated or corrugated
touched it. Precautions to minimize the problems with hydro-
metal oven chambers, and back pressure/flow controlled
gen exiting the split vent or septum purge include:
pneumatics,whichminimizethehazardswhenusinghydrogen
(a)Plumbing the exit lines to a hood or venting the
carrier gas. Additional precautions used by analysts include:
escaping gas outside,
(a)Frequently check for carrier gas leaks using a sensi-
(b)Plumbing the lines to exit into a vial of water, and
tive electronic leak detector,
(c)Plumbing the exit lines to a position where analysts
(b)Use electronic sensors that shut down the carrier gas
couldnotgetburnedorafirecouldnotbestartedifinadvertent
flow should an explosive atmosphere be detected,
ignition occurred.
(c)Purge an inert gas (N ) into the oven chamber to
7.2.3 Flow-Regulated Pneumatics—Fig.6illustratesaflow-
displace oxygen and prevent an explosive atmosphere from
regulated back pressure system commonly used today for
forming, and
split/splitless inlets. A flow controller positioned upstream of
(d)Minimize the amount of carrier gas that could be theinjectorservestocontrolthetotalamountofcarriergasthat
expelled in the oven chamber if a leak were to occur by
is expelled from the split vent, septum purge, and column.The
installing a needle valve, restrictor, or flow controller prior to back pressure regulator stops or reduces flow from exiting the
the carrier inlet bulkhead fitting (head pressure regulated
split vent until the desired column head pressure is reached.
systems only). The flow controller, sensing that no flow is exiting the split
(2) Warning—Analysts should also be aware that hydro-
vent, provides the increase of pressure necessary to meet the
gen will be expelled from both the split vent and septum purge requirementsofthebackpressureregulator.Thus,itistheback
when it is used as a carrier gas. Because of the fast diffusivity pressure regulator, which is located downstream of the split
of hydrogen, an explosion in a laboratory setting is highly point,thatactuallycontrolsthecapillarycolumnflowrate.One
E1510−95 (2021)
flow and subsequent damage to all capillary columns in the
entiresystem.Topreventthisfromhappening,limittheflowof
carriergastoeachgaschromatograph(bymeansofathrottling
valve) until it matches the flow requirements of your inlet
system. This throttle point can be detected when the column’s
head pressure starts to decrease if the throttling valve is closed
any further.
7.2.5 Injector Maintenance—Maintenance should be per-
formedontheinjectorpriortoinstallingacapillarycolumnand
periodically, depending on the number of injections made and
FIG. 6Flow-Regulated Back Pressure System the cleanliness of the samples. Maintenance should include
cleaning and deactivating inlet sleeves, replacing critical inlet
seals, and replacing the septum. Review the instrument manu-
of the primary benefits of a flow-controlled/back pressure-
al’s inlet diagram prior to disassembly.
regulated system is that adjustments to the capillary column
7.2.6 Cleaning and Deactivating Injector Sleeves—The in-
flowrate(bymeansofheadpressurechanges)donotaffectthe
letsleeveshouldbefreefromseptumparticles,sampleresidue,
amount of carrier gas exiting the splitter vent. Thus, once the
and ferrule fragments to obtain optimum column performance.
desired split vent flow rate is achieved, analysts should not
The inlet sleeve must be deactivated when analyzing samples
have to change the flow controller setting when installing
with active functional groups such as alcohols, acids,
different columns.
aldehydes, phenols, bases, or other compounds prone to
7.2.3.1 Flow-regulated back pressure systems prevent a
decomposition or adsorption on untreated glass surfaces. If the
drastic carrier gas loss that could occur if an inlet fitting or
sleeve is deactivated and not excessively dirty, it may be
column leak were to occur. Leaks are indicated by a failure to
cleaned with organic solvents without affecting the integrity of
obtain the proper column operating pressure by adjusting the
the deactivated layer. First, use non-swelling organic solvents
back pressure regulators.Acommon mistake made by analysts
suchasmethanolorisopropylalcoholtoremoveseptaparticles
not familiar with flow-regulated back pressure systems is to
that adhere to the sleeve wall. Then use solvents such as
increasethetotalsystemflowbyturninguptheflowcontroller
pentane, methylene chloride, toluene, or any other solvent that
(splitventadjustmentknob)whenaproperheadpressurecan’t
willsolubilizeandremovesampleresidue.Nylontubebrushes
be obtained rather than checking for inlet leaks.
and pipe cleaners are ideal for cleaning sleeves. Do not use
7.2.4 Head Pressure-Regulated Pneumatic Systems—Fig. 7
illustrates a head pressure regulated inlet system used in some laboratory detergents, acids, or bases to clean sleeves. This
split/splitless inlet systems.Asingle stage pressure regulator is
removes the deactivation layer and requires re-silanization of
used to control the flow rate in the capillary column by the sleeve.
increasing or decreasing the upstream inlet pressure. The split
7.2.6.1 Sleeves that are very dirty or contain pyrolyzed
vent and septum purge flow rates are controlled by a needle
residue can be difficult to clean and may not justify the cost to
valve or variable restrictor, downstream of the pressure regu-
doso.Heatingsleeves(borosilicateorquartzglass)inamuffle
lator.Headpressuresystemsrequirereadjustmentoftheneedle
furnace at 550°C overnight will remove most contaminants.
valve controlling the septum purge or split vent every time a
Etchingwitha1to1to1mixtureofhydrofluoricacid,sulfuric
change is made in the column’s head pressure.
acid, and deionized water for 10 s is also very effective.
7.2.4.1 It is recommended that a throttling valve (needle
7.2.6.2 High–quality deactivated sleeves are available from
valve or restrictor) be placed on the carrier gas inlet bulkhead
some capillary and instrument suppliers. If deactivated sleeves
fitting of pressure-regulated systems to prevent a catastrophic
arenotavailable,theycanbedeactivatedbyusingathree–step
carrier gas loss should an inlet leak occur. If several GCs are
procedure: acid cleaning, dehydration, and silanization.
attached to a common carrier gas source, a leak in one GC
7.2.7 Acid Cleaning—The first step involves etching the
coulddrainthecarriergasfromallotherGCs,causingalossof
sleeves in an acid solution (such as 1 to 1 to 1 sulfuric/
hydrofluoric/deionized water) for a 10-s duration. Then rinse
the sleeves thoroughly with deionized water and blow dry (do
not use methanol or acetone to help the drying process).
(Warning—Exert extreme caution when using hydrofluoric
acid. Only professionals properly trained and equipped with
the appropriate safety devices should attempt to handle strong
acids. Hydrofluoric acid could cause severe burns and nerve
damage if it comes in contact with skin, is ingested, or
inhaled.)
7.2.7.1 Dehydration—Thesecondstepinvolvestheremoval
of surface water. Heat the sleeves in an oven at 250°C for 1 h.
Program slowly (approximately 4°C/min) from ambient to
FIG. 7Head Pressure Regulated System 250°C to prevent water staining or spotting.
E1510−95 (2021)
7.2.7.2 Silanization—The third step involves a reaction of bracketsalsoproperlypositionthecolumnintheovenchamber
the glass surface silanol groups with a chlorosilane to prevent to reduce thermal gradients that enhance retention time repro-
them from adsorbing or degrading sample compounds. Si- ducibility. If there is not a column support bracket, one can be
lanization should be performed within 1 h after the sleeves made by inserting a temperature-resistant peg board rod into
have cooled from the dehydration process to prevent re- thecorrugatedovenwallorbyhavingan“S”hookwith ⁄16in.
adsorptionofatmosphericmoisture.Soakthesleevesfor5min tube hanging from the oven ceiling. Be careful not to damage
in a 5% volume to volume mixture of dimethyldichlorosilane theoventhermocoupleorinterferewiththefanoperationwhen
intoluene.Rinsethoroughlywithtoluenetoremovetheexcess making homemade brackets, and do not allow fused silica to
chlorosilane reagent. Finally, any unreacted chlorine groups contact metal parts. Once the column is mounted, uncoil two
should be capped by soaking for 5 min in methanol. Blow dry loops of fused silica tubing from the cage to provide adequate
after removing from the methanol. The sleeves are now ready lengthforinstallationwiththeappropriateferrulesandfittings.
to be used. (Warning—Exert caution when handling chlorosi- 7.2.13 Choosing Ferrules—Usually graphite or Vespel
lanes. Chlorosilanes give off HCl vapors when reacted with graphiteferrulesareusedtosealthecolumntotheinjectorand
silanol groups, methanol, or if it comes in contact with detector in capillary gas chromatography. Both ferrule types
atmospheric moisture. Only professionals properly trained and have advantages and disadvantages. Because graphite ferrules
equipped with the appropriate safety devices should attempt to are soft, they easily conform to all column–outside diameters
handle chlorosilanes.) and different types of instrument–fitting configurations.
However, they can flake or fragment upon removal, causing
7.2.8 Protection Against Dirty Samples—Precautions such
particles to lodge in the injector or detector sleeves. Vespel/
as packing sleeves with a small plug of fused silica wool
graphite ferrules are hard and must match the column and
should be employed when analyzing samples containing high
fitting dimensions closely to seal properly. In addition, Vespel/
molecular weight residue or particulates. Use fused silica or
graphite ferrules can deform and shrink upon initial heating
glass wool cautiously because, if not deactivated properly, it
and subsequently should be re-tightened or leakage will occur.
could degrade the system’s inertness to sensitive compounds
Vespel/graphite ferrules do not shed fragments and can be
prone to breaking down in hot inlets. Alternative sleeve
reused many times.Always check the upper temperature limit
designs, which minimize interaction of the sample with non-
of the ferrule for your application.
volatileresidue,areavailablefromsomecapillarymanufactur-
7.2.13.1 Graphite ferrules are the easiest to use, because
ers. See 8.3 for more information about analyzing dirty
they are leak-free, universal for most systems, and the choice
samples.
for most beginning capillary chromatographers. Vespel/
7.2.9 Replacing Critical Seals—ReviewtheGCmanualand
graphite ferrules are preferred for use in mass spectrometers
replace the critical seal prior to reinstalling the inlet sleeve.
since they do not flake and contaminate the ion source with
Most capillary injection ports use a rubber O-ring or graphite
particles. In all cases, it is best to choose a ferrule that will fit
ferrule to seal the sleeve inside the injection port body. It is
snugly on or be slightly larger than the outer diameter of the
critical that the seal fits tightly around the sleeve and prevents
capillary tubing used. This minimizes the need for excessive
the carrier gas from leaking around the outside of the sleeve.
torque in order to properly seal the ferrule to the column.
7.2.10 Changing Septa—Replace the septum frequently
7.2.14 Cutting Column Ends—Fused silica tubing breaks
(usually before 100 injections) to prevent leaks and fragmen-
easily when the outside polyimide layer is scratched or scored.
tation. Otherwise, multiple injections and continuous exposure
An improper cut allows polyimide or glass fragments to
to a hot injection port will decompose the septum, causing
interactwiththesamplestreamanddegradetheinertnessofthe
particles to fall into the inlet sleeve. These particles are a
system. Scoring devices that utilize a blade are preferred over
potential source of ghost peaks, loss of inertness, and carrier
pointed ones because a better, squarer cut is made. Silica
gas flow occlusion. It is best to install a new septum at the end
scoring wafers, sapphire blades, or tungsten carbide scoring
ofananalyticalsequencesoitcanconditionintheinjectorand
blades usually produce the best cuts and are available from
reducetheincidenceofghostpeaks.Alwaysuseahigh-quality,
most common suppliers.
low-bleed septum to prevent the ghost peaks from interfering
7.2.14.1 To obtain a square cut, place the column end
with the compounds of interest. Never handle septa with bare
againsttheforefingerandscorethepolyimidelayerlightlyand
hands. Always use forceps to avoid contamination.
rapidly. Score only one side of the column. Point the column
7.2.11 Setting Detector and Make-up Gas Flow Rates—
end down (to prevent glass shards from falling inside) and
Confirm that the make-up gas, detector fuel, and oxidant flow
quickly flick the column just above the score. Examine the
rates are set according to the instrument manual’s specifica-
quality of the cut with a small 10× pocket magnifier and make
tions.Someinstrumentsdonothaveleak-tightdetectorcavities
sure the cut is clean and square. See Fig. 8 for a good versus
andrequireflow-rateverificationbeforethecolumnisinstalled
poor column cut. It may require several cuts to obtain one that
into the detector. However, for GCs with leak-tight detector
is square and desirable. Use an old column to practice and
cavities, it is usually easier to check detector and make-up gas
develop the skill needed to consistently make square cuts.
flow rates after the column is installed.
7.2.15 Installing the Connecting Nut and Ferrule—
7.2.12 Mounting the Column in the Oven—Most instrument
Capillary columns are usually shipped from the manufacturer
manufacturersprovideuniversalhangingbracketsthatholdthe
column in the center of the oven and prevent the fused silica
tubing from abrading or rubbing against the oven wall. The Vespel is a registered trademark of the DuPont Company.
E1510−95 (2021)
NOTE 1—This photo shows a good and bad column cut. The good cut
leaves the end of the column square and free of fragments or fractures.
FIG. 8Good Versus Bad Column Cut
NOTE 1—Rubber-tipped slide-lock tweezers hold the column firmly at
the correct distance during installation.
FIG. 9Different Measuring Techniques
with the ends flame-sealed or capped with septa. Cut approxi-
mately 10 cm off of each end as described in 7.2.14. Install the
7.2.16.2 Make sure the fused silica tubing is not sharply
inlet–connecting nut followed by the appropriately sized fer-
bent when installing the column. The tubing should gently
ruleinthemannerdescribedintheinstrumentmanual.Besure
bend from the cage to the fitting in angles less than 90° or a
to point the column end down when installing the ferrule to
diameter less than 15 cm. Sharp bends weaken the fused silica
prevent shards from falling into the capillary bore. Slide the
andeventuallycausespontaneousbreakagewhilebeingusedin
connecting nut and ferrule approximately 20 cm down the
the oven (see Fig. 10). If the tubing cannot be positioned to
length of the column to make installation easier. Cut an
avoid sharp bends, repeat the installation process (7.2.13) and
additional
...