ASTM E260-96(2001)
(Practice)Standard Practice for Packed Column Gas Chromatography
Standard Practice for Packed Column Gas Chromatography
SCOPE
1.1 This practice is intended to serve as a general guide to the application of gas chromatography (GC) with packed columns for the separation and analysis of vaporizable or gaseous organic and inorganic mixtures and as a reference for the writing and reporting of GC methods.
Note 1--This practice excludes any form of gas chromatography associated with open tubular (capillary) columns.
1.2 This standard does not purport to address all the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8 and 9.1.3.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E260–96(Reapproved 2001)
Standard Practice for
Packed Column Gas Chromatography
This standard is issued under the fixed designation E260; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope CGA P-9 The Inert Gases: Argon, Nitrogen and Helium
CGAV-7 Standard Method of Determining Cylinder Valve
1.1 This practice is intended to serve as a general guide to
Outlet Connections for Industrial Gas Mixtures
the application of gas chromatography (GC) with packed
CGA P-12 Safe Handling of Cryogenic Liquids
columns for the separation and analysis of vaporizable or
HB-3 Handbook of Compressed Gases
gaseous organic and inorganic mixtures and as a reference for
the writing and reporting of GC methods.
3. Terminology
NOTE 1—This practice excludes any form of gas chromatography
3.1 Terms and relations are defined in Practice E355 and
associated with open tubular (capillary) columns.
references therein.
1.2 This standard does not purport to address all the safety
4. Summary of Practice
concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and 4.1 Ablock diagram of the basic apparatus needed for a gas
health practices and determine the applicability of regulatory
chromatographic system is as shown in Fig. 1. An inert,
limitations prior to use.Specifichazardstatementsaregivenin pressure or flow-controlled carrier gas flowing at a measured
Section 8 and 9.1.3.
rate passes to the injection port or gas sample valve.Asample
isintroducedintotheinjectionport,whereitisvaporized,orif
2. Referenced Documents
gaseous, into a gas sample valve, and then swept into and
2.1 ASTM Standards:
through the column by the carrier gas. Passage through the
E355 Practice for Gas Chromatography Terms and Rela-
column separates the sample into its components. The effluent
tionships
from the column passes to a detector where the response of
E516 Practice for Testing Thermal Conductivity Detectors
sample components is measured as they emerge from the
Used in Gas Chromatography
column. The detector electrical output is relative to the
E594 Practice forTesting Flame Ionization Detectors Used
concentrationofeachresolvedcomponentandistransmittedto
in Gas Chromatography
a recorder, or electronic data processing system, or both, to
E697 PracticeforUseofElectronCaptureDetectorsinGas
produce a record of the separation, or chromatogram, from
Chromatography
which detailed analysis can be obtained. The detector effluent
E840 Practice for Using Flame Photometric Detectors in
must be vented to a hood if the effluent contains toxic
Gas Chromatography
substances.
E1140 Practice for Testing Nitrogen/Phosphorus Thermi-
4.2 Gas chromatography is essentially a physical separation
onicIonizationDetectorsforUseinGasChromatography
technique.Theseparationisobtainedwhenthesamplemixture
2.2 CGA Publications:
in the vapor phase passes through a column containing a
CGA P-1 Safe Handling of Compressed Gases in Contain-
stationary phase possessing special adsorptive properties. The
ers
degree of separation depends upon the differences in the
CGAG-5.4 Standard for Hydrogen Piping Systems at Con-
distribution of volatile compounds, organic or inorganic, be-
sumer Locations
tween a gaseous mobile phase and a selected stationary phase
that is contained in a tube or GC column. In gas-liquid
chromatography (GLC), the stationary phase is a nonvolatile
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
liquid or gum coated as a thin film on a finely-divided, inert
Spectroscopy and is the direct responsibility of Subcommittee E13.19 on Chroma-
supportofarelativelylargesurfacearea,andthedistributionis
tography.
Current edition approved April 10, 1996. Published June 1996. Originally
based on partition. The liquid phase should not react with, and
published as E260–65T. Last previous edition E260–96.
should have different partition coefficients for, the various
Annual Book of ASTM Standards, Vol 3.06.
Available from Compressed Gas Association, Inc., 1725 Jefferson Davis
Highway, Arlington, VA 22202-4100.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E260
FIG. 1 Block Diagram of a Basic Gas Chromatographic System
components in the sample. In gas-solid chromatography conductivitydetectors,eitherthepeakareasorthepeakheights
(GSC), the stationary phase is a finely divided solid adsorbent are proportional to the concentration of the components in the
(see 4.4). sample within the linear range of the detector system. How-
4.2.1 After separation in the analytical column, the compo- ever, response fractors are not necessarily the same for all
nents are detected, and the detector signal is related to the compounds, and linearity of detector response may depend on
concentration of the volatile components. Tentative identifica- operating conditions. (Testing of detector performance is
tions can be made by comparison with the retention times of discussed in ASTM Standard Practices for the appropriate
known standards under the same conditions, either on a single detector, see 2.1).
columnorpreferablybyinjectingthesampleontotwocolumns
4.6 Components in a mixture may be tentatively identified
of different selectivity. Ancillary techniques, such as mass
by retention time. Ideally, each substance has a unique reten-
spectrometry or infrared spectrophotometry, are generally nec-
tion time in the chromatogram for a specific set of operating
essary for positive identification of components in samples.
conditions. However, caution is required because the GC
4.2.2 Prior to performing a GC analysis, the following
separation may be incomplete and a single peak may represent
parameters must be considered:
more than one compound. This is especially true of unknown
4.2.2.1 Sample preparation.
mixtures and complex mixtures because of the very large
4.2.2.2 Stationary phase and loading on support.
number of possible compounds in existence and the finite
4.2.2.3 Column material required.
number of peaks that a chromatograph might resolve. Addi-
4.2.2.4 Solid support and mesh size.
tional characterization data may be provided by ancillary
4.2.2.5 Column length and diameter.
techniques, such as spectrometry.
4.2.2.6 Instrument and detector type that will be needed.
4.2.2.7 Injector, column oven, and detector temperatures
5. Significance and Use
required for analysis.
5.1 This practice describes a procedure for packed-column
4.2.2.8 Injection techniques, such as flash volatilization,
gas chromatography. It provides general comments, recom-
on-column technique, purge and trap, pyrolysis, etc.
mended techniques, and precautions.Arecommended form for
4.2.2.9 Carrier gas and flow rate.
reporting GC methods is given in Section 14.
4.2.2.10 Data handling and presentation.
4.3 In gas-liquid chromatography, the degree of separation
6. Apparatus
possible between any two compounds (solutes), is determined
6.1 Carrier Gas System—Common carrier gases are helium
by the ratio of their partition coefficients and the separation
and nitrogen. Paragraph 7.6 provides more details on carrier
efficiency.The partition coefficient, K, is the ratio of the solute
gases.Meansmustbeprovidedtomeasureandcontroltheflow
concentration in the liquid phase to the solute concentration in
rate of the carrier gas. Any flow or pressure control and
the vapor phase at equilibrium conditions. The partition coef-
measurement combination may be used that will give an
ficientisaffectedbytemperatureandthechemicalnatureofthe
accurately known and reproducible flow rate over the desired
solute (sample) and solvent (stationary phase).
range.
4.4 Another mechanism for separation is gas-solid chroma-
tography. With this technique there is no liquid phase, only a 6.1.1 The main gas supply is regulated with a two-stage
porous polymer, molecular sieve, or solid adsorbent. Partition regulator which must have a stainless steel diaphragm. Rubber
is accomplished by distribution between the gas phase and the orplasticdiaphragmspermitoxygenorwatertodiffuseintothe
solid phase. carrier gas. In addition, instruments will have a flow controller
4.5 After the sample is resolved into individual components between the pressure regulator and column inlet to maintain a
by the chromatographic column, the concentration or mass constant flow during temperature programming. Copper or
flow of each component in the carrier gas can be measured by stainless steel carrier gas lines, not plastic tubing, should be
an appropriate detector which sends an electrical signal to a used to avoid diffusion of oxygen (air) into the carrier gas.
recording potentiometer or other readout device. The curve Whenusingthethermalconductivitydetector,variationsinthe
obtained by plotting detector response against time is referred flow will change retention and response. The carrier gas line
to as a chromatogram. For flame ionization and thermal pressure must be higher than that required to maintain the
E260
column flow at the upper temperature limit for the flow inlet usually has a somewhat higher thermal mass than an
controller to operate properly. A pressure of 40 to 60 psi is equivalent sector of the rest of the column, the inlet must be
usually sufficient. heated somewhat above the maximum analysis temperature of
the column oven. The criteria of good peak shape and
6.2 Column Temperature Control—Precise column tem-
quantitation should be used to determine the maximum re-
peraturecontrolismandatoryifreproducibleanalysesaretobe
quired temperature for the inlet. One should consider the
obtained. Temperature control must be within 0.1°C if reten-
temperature limit of the column packing when heating the
tion times are to be compared with another instrument.
injection inlet and detector. With some samples, a nonheated
6.2.1 Air Bath—The thermostated forced-air bath is gener-
injection port is adequate, especially with temperature-
ally accepted as the best practical method of temperature
programmed operation.
regulation for most applications. Temperatures can be con-
trolled by regulators or proportionally controlled heaters using 6.3.4 Injection Port Septum:
a thermocouple or platinum-resistance thermometer as a sens-
6.3.4.1 The septum is a disc, usually made of silicone
ing element.The advantage of a forced-air bath is the speed of
rubber,whichsealsoneendoftheinjectionport.Itisimportant
temperature equilibration.Air bath ovens are readily adaptable
to change the septum frequently after two to three dozen
to temperature programming and are capable of operating over
injections,orpreferablyattheendoftheworkingday.Thebest
a range of 35 to 450°C. This range can be extended down
technique is to change the septum when the column is
to−100°C by using cryogenic equipment.
relatively cool (below 50°C) to avoid contact of stationary
6.2.2 Other Devices—Liquid baths, drying ovens, incuba-
phase in a hot column with air (danger of oxidation).After the
tors, or vapor jacket enclosures are less stable, less convenient
septum is changed, return the inlet temperature to that which
means of providing a source of heat to maintain or raise the
was originally set. The inlet temperature should be the opti-
temperature of a chromatographic column. These devices are
mum for the particular analysis, as well as within the recom-
not recommended for precision chromatographic applications.
mended operating temperature of the septum. If the septum is
6.3 The Injection Port—The purpose of the injection port is
punctured too many times, it will leak air into the gas
to introduce the sample into the gas chromatographic column chromatographic system, even though it is under pressure. At
by instantaneous volatilization following injection into the gas high temperatures, above 150 to 200°C, air (oxygen) in the
chromatographic system. Two sample inlet types are in com- carrier gas from a septum leak will degrade the stationary
mon use in gas chromatography: the flash vaporization and the phase.An excessive septum leak will also produce a change in
on-column injection inlets. carrier gas flow rate (a change in retention time) and loss of
sample (irreproducible peak heights) due to outflow from the
6.3.1 The temperature of the flash vaporization inlet should
leak. When installing the septum, do not overtighten the
be above the boiling points of the sample components and is
retaining nut. The septa will swell at high temperature and
limited by the amount of septum bleed generated and the
extrudeoutoftheinjectionport.Asnugfitatroomtemperature
temperature stability of sample components. It should be set at
is sufficient. It is important for septum life to make sure the
that temperature above which no improvement in peak shape
injection needle is sharp with no bent tip. Fine emery cloth, or
occurs but should be determined by the nature of the sample
a fine sharpening stone, can be used to sharpen the point.
andthevolumeinjected,notbythetemperatureofthecolumn.
If the inlet temperature is too low, broad peak with a slowly
6.3.4.2 Ghost peaks may be observed in temperature pro-
rising front edge will result from slow vaporization of the
grammed runs due to septum bleed. Septum bleed is due to the
sample. If the temperature is set far above what is necessary to
thermal decomposition, 300°C or higher, of the septum that
produce fast vaporization, thermal decomposition of the
produces primarily lower molecular weight cyclic dimethylsi-
sample, decreased septum life, and ghost peaks due to septum
loxanes. It contributes to baseline response and is frequently
bleed may be observed. Generally, a good guideline is to
observedasevenlyspacedpeaksinatemperatureprogrammed
maintain the inlet temperature 25 to 30°C higher than the
runinwhichnosamplehasbeeninjected.Thissituationcanbe
highest boiling point of any sample component.
demonstratedbythedisappearanceofghostpeaksafterplacing
aluminum foil (pre-cleaned with solvents such as methylene
6.3.2 A glass liner placed inside the injection port will
chloride or toluene) over the inner face of the septum or by
eliminatesamplecontactwithhotmetalinnerwallsoftheinlet,
turning off the injector temperature and making several blank
which can catalyze thermal decompositions.Any debris left in
runs. Septum bleed can be decreased by using either air- or
theliner,especiallyfrombiologicalsamples,canbeasourceof
water-cooled septum retaining n
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