ASTM E260-96(2011)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E260 − 96 (Reapproved 2011)
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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope CGAG-5.4Standard for Hydrogen Piping Systems at Con-
sumer Locations
1.1 This practice is intended to serve as a general guide to
CGAP-9The Inert Gases: Argon, Nitrogen and Helium
the application of gas chromatography (GC) with packed
CGAP-12Safe Handling of Cryogenic Liquids
columns for the separation and analysis of vaporizable or
CGAV-7Standard Method of Determining Cylinder Valve
gaseous organic and inorganic mixtures and as a reference for
Outlet Connections for Industrial Gas Mixtures
the writing and reporting of GC methods.
HB-3Handbook of Compressed Gases
NOTE 1—This practice excludes any form of gas chromatography
associated with open tubular (capillary) columns.
3. Terminology
1.2 This standard does not purport to address all the safety
3.1 Terms and relations are defined in Practice E355 and
concerns, if any, associated with its use. It is the responsibility
references therein.
of the user of this standard to establish appropriate safety and
health practices and determine the applicability of regulatory
4. Summary of Practice
limitations prior to use.Specifichazardstatementsaregivenin
Section 8 and 9.1.3.
4.1 Ablock diagram of the basic apparatus needed for a gas
chromatographic system is as shown in Fig. 1. An inert,
2. Referenced Documents
pressure or flow-controlled carrier gas flowing at a measured
rate passes to the injection port or gas sample valve.Asample
2.1 ASTM Standards:
isintroducedintotheinjectionport, whereit isvaporized,orif
E355Practice for Gas ChromatographyTerms and Relation-
gaseous, into a gas sample valve, and then swept into and
ships
through the column by the carrier gas. Passage through the
E516Practice for Testing Thermal Conductivity Detectors
column separates the sample into its components. The effluent
Used in Gas Chromatography
from the column passes to a detector where the response of
E594Practice for Testing Flame Ionization Detectors Used
sample components is measured as they emerge from the
in Gas or Supercritical Fluid Chromatography
column. The detector electrical output is relative to the
E697Practice for Use of Electron-Capture Detectors in Gas
concentrationofeachresolvedcomponentandistransmittedto
Chromatography
a recorder, or electronic data processing system, or both, to
E840PracticeforUsingFlamePhotometricDetectorsinGas
produce a record of the separation, or chromatogram, from
Chromatography
which detailed analysis can be obtained. The detector effluent
E1140PracticeforTestingNitrogen/PhosphorusThermionic
must be vented to a hood if the effluent contains toxic
Ionization Detectors for Use In Gas Chromatography
substances.
2.2 CGA Publications:
4.2 Gas chromatography is essentially a physical separation
CGAP-1SafeHandlingofCompressedGasesinContainers
technique.Theseparationisobtainedwhenthesamplemixture
in the vapor phase passes through a column containing a
stationary phase possessing special adsorptive properties. The
This practice is under the jurisdiction ofASTM Committee E13 on Molecular
degree of separation depends upon the differences in the
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
mittee E13.19 on Separation Science.
distribution of volatile compounds, organic or inorganic, be-
Current edition approved Nov. 1, 2011. Published December 2011. Originally
tween a gaseous mobile phase and a selected stationary phase
approved in 1965. Last previous edition approved in 2006 as E260–96(2011).
that is contained in a tube or GC column. In gas-liquid
DOI: 10.1520/E0260-96R11.
chromatography (GLC), the stationary phase is a nonvolatile
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
liquid or gum coated as a thin film on a finely-divided, inert
Standards volume information, refer to the standard’s Document Summary page on
supportofarelativelylargesurfacearea,andthedistributionis
the ASTM website.
based on partition. The liquid phase should not react with, and
Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5th
Floor, Chantilly, VA 20151-2923, http://www.cganet.com. should have different partition coefficients for, the various
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E260 − 96 (2011)
FIG. 1 Block Diagram of a Basic Gas Chromatographic System
components in the sample. In gas-solid chromatography to as a chromatogram. For flame ionization and thermal
(GSC), the stationary phase is a finely divided solid adsorbent conductivitydetectors,eitherthepeakareasorthepeakheights
(see 4.4). are proportional to the concentration of the components in the
4.2.1 After separation in the analytical column, the compo- sample within the linear range of the detector system.
nents are detected, and the detector signal is related to the However, response fractors are not necessarily the same for all
concentration of the volatile components. Tentative identifica- compounds, and linearity of detector response may depend on
tions can be made by comparison with the retention times of operating conditions. (Testing of detector performance is
known standards under the same conditions, either on a single discussed in ASTM Standard Practices for the appropriate
columnorpreferablybyinjectingthesampleontotwocolumns detector, see 2.1).
of different selectivity. Ancillary techniques, such as mass
4.6 Components in a mixture may be tentatively identified
spectrometry or infrared spectrophotometry, are generally nec-
by retention time. Ideally, each substance has a unique reten-
essary for positive identification of components in samples.
tion time in the chromatogram for a specific set of operating
4.2.2 Prior to performing a GC analysis, the following
conditions. However, caution is required because the GC
parameters must be considered:
separation may be incomplete and a single peak may represent
4.2.2.1 Sample preparation.
more than one compound. This is especially true of unknown
4.2.2.2 Stationary phase and loading on support.
mixtures and complex mixtures because of the very large
4.2.2.3 Column material required.
number of possible compounds in existence and the finite
4.2.2.4 Solid support and mesh size.
number of peaks that a chromatograph might resolve. Addi-
4.2.2.5 Column length and diameter.
tional characterization data may be provided by ancillary
4.2.2.6 Instrument and detector type that will be needed.
techniques, such as spectrometry.
4.2.2.7 Injector, column oven, and detector temperatures
required for analysis.
5. Significance and Use
4.2.2.8 Injection techniques, such as flash volatilization,
5.1 This practice describes a procedure for packed-column
on-column technique, purge and trap, pyrolysis, etc.
gas chromatography. It provides general comments, recom-
4.2.2.9 Carrier gas and flow rate.
mended techniques, and precautions.Arecommended form for
4.2.2.10 Data handling and presentation.
reporting GC methods is given in Section 14.
4.3 In gas-liquid chromatography, the degree of separation
possible between any two compounds (solutes), is determined
6. Apparatus
by the ratio of their partition coefficients and the separation
6.1 Carrier Gas System—Common carrier gases are helium
efficiency.The partition coefficient, K, is the ratio of the solute
andnitrogen.7.6providesmoredetailsoncarriergases.Means
concentration in the liquid phase to the solute concentration in
must be provided to measure and control the flow rate of the
the vapor phase at equilibrium conditions. The partition coef-
carrier gas. Any flow or pressure control and measurement
ficientisaffectedbytemperatureandthechemicalnatureofthe
combination may be used that will give an accurately known
solute (sample) and solvent (stationary phase).
and reproducible flow rate over the desired range.
4.4 Another mechanism for separation is gas-solid chroma-
6.1.1 The main gas supply is regulated with a two-stage
tography. With this technique there is no liquid phase, only a
regulator which must have a stainless steel diaphragm. Rubber
porous polymer, molecular sieve, or solid adsorbent. Partition
orplasticdiaphragmspermitoxygenorwatertodiffuseintothe
is accomplished by distribution between the gas phase and the
carrier gas. In addition, instruments will have a flow controller
solid phase.
between the pressure regulator and column inlet to maintain a
4.5 After the sample is resolved into individual components constant flow during temperature programming. Copper or
by the chromatographic column, the concentration or mass stainless steel carrier gas lines, not plastic tubing, should be
flow of each component in the carrier gas can be measured by used to avoid diffusion of oxygen (air) into the carrier gas.
an appropriate detector which sends an electrical signal to a Whenusingthethermalconductivitydetector,variationsinthe
recording potentiometer or other readout device. The curve flow will change retention and response. The carrier gas line
obtained by plotting detector response against time is referred pressure must be higher than that required to maintain the
E260 − 96 (2011)
column flow at the upper temperature limit for the flow temperature is controlled. In practice, because an on-column
controller to operate properly. A pressure of 40 to 60 psi is inlet usually has a somewhat higher thermal mass than an
usually sufficient. equivalent sector of the rest of the column, the inlet must be
heated somewhat above the maximum analysis temperature of
6.2 Column Temperature Control—Precisecolumntempera-
the column oven. The criteria of good peak shape and
ture control is mandatory if reproducible analyses are to be
quantitation should be used to determine the maximum re-
obtained. Temperature control must be within 0.1°C if reten-
quired temperature for the inlet. One should consider the
tion times are to be compared with another instrument.
temperature limit of the column packing when heating the
6.2.1 Air Bath—The thermostated forced-air bath is gener-
injection inlet and detector. With some samples, a nonheated
ally accepted as the best practical method of temperature
injection port is adequate, especially with temperature-
regulation for most applications. Temperatures can be con-
programmed operation.
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,
phase in a hot column with air (danger of oxidation).After the
incubators, or vapor jacket enclosures are less stable, less
septum is changed, return the inlet temperature to that which
convenient means of providing a source of heat to maintain or
was originally set. The inlet temperature should be the opti-
raise the temperature of a chromatographic column. These
mum for the particular analysis, as well as within the recom-
devices are not recommended for precision chromatographic
mended operating temperature of the septum. If the septum is
applications.
punctured too many times, it will leak air into the gas
6.3 The Injection Port—The purpose of the injection port is
chromatographic system, even though it is under pressure. At
to introduce the sample into the gas chromatographic column
high temperatures, above 150 to 200°C, air (oxygen) in the
by instantaneous volatilization following injection into the gas
carrier gas from a septum leak will degrade the stationary
chromatographic system. Two sample inlet types are in com-
phase.An excessive septum leak will also produce a change in
mon use in gas chromatography: the flash vaporization and the
carrier gas flow rate (a change in retention time) and loss of
on-column injection inlets.
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.
6.3.4.2 Ghost peaks may be observed in temperature pro-
If the inlet temperature is too low, broad peak with a slowly
grammed runs due to septum bleed. Septum bleed is due to the
rising front edge will result from slow vaporization of the
thermal decomposition, 300°C or higher, of the septum that
sample. If the temperature is set far above what is necessary to
produces primarily lower molecular weight cyclic dimethylsi-
produce fast vaporization, thermal decomposition of the
loxanes. It contributes to baseline response and is frequently
sample, decreased septum life, and ghost peaks due to septum
observedasevenlyspacedpeaksinatemperatureprogrammed
bleed may be observed. Generally, a good guideline is to
runinwhichnosamplehasbeeninjected.Thissituationcanbe
maintain the inlet temperature 25 to 30°C higher than the
demonstratedbythedisappearanceofghostpeaksafterplacing
highest boiling point of any sample component.
aluminum foil (pre-cleaned with solvents such as methylene
6.3.2 A glass liner placed inside the injection port will
chloride or toluene)
...