1、Designation: E 260 96 (Reapproved 2006)Standard Practice forPacked Column Gas Chromatography1This standard is issued under the fixed designation E 260; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is intended to serve as a general guide tothe application of gas chromatography (GC) with packedcolumns for the separation
3、 and analysis of vaporizable orgaseous organic and inorganic mixtures and as a reference forthe writing and reporting of GC methods.NOTE 1This practice excludes any form of gas chromatographyassociated with open tubular (capillary) columns.1.2 This standard does not purport to address all the safety
4、concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use. Specific hazard statements are given inSection 8 and 9.1.3.2. Referenced Document
5、s2.1 ASTM Standards:2E 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 516 Practice for Testing Thermal Conductivity DetectorsUsed in Gas ChromatographyE 594 Practice for Testing Flame Ionization Detectors Usedin Gas or Supercritical Fluid ChromatographyE 697 Practice for Use of Electr
6、on-Capture Detectors inGas ChromatographyE 840 Practice for Using Flame Photometric Detectors inGas ChromatographyE 1140 Practice for Testing Nitrogen/Phosphorus Thermi-onic Ionization Detectors for Use In Gas Chromatography2.2 CGA Publications:3CGA P-1 Safe Handling of Compressed Gases in Contain-e
7、rsCGA G-5.4 Standard for Hydrogen Piping Systems at Con-sumer LocationsCGA P-9 The Inert Gases: Argon, Nitrogen and HeliumCGA V-7 Standard Method of Determining Cylinder ValveOutlet Connections for Industrial Gas MixturesCGA P-12 Safe Handling of Cryogenic LiquidsHB-3 Handbook of Compressed Gases3.
8、Terminology3.1 Terms and relations are defined in Practice E 355 andreferences therein.4. Summary of Practice4.1 Ablock diagram of the basic apparatus needed for a gaschromatographic system is as shown in Fig. 1. An inert,pressure or flow-controlled carrier gas flowing at a measuredrate passes to th
9、e injection port or gas sample valve. A sampleis introduced into the injection port, where it is vaporized, or ifgaseous, into a gas sample valve, and then swept into andthrough the column by the carrier gas. Passage through thecolumn separates the sample into its components. The effluentfrom the co
10、lumn passes to a detector where the response ofsample components is measured as they emerge from thecolumn. The detector electrical output is relative to theconcentration of each resolved component and is transmitted toa recorder, or electronic data processing system, or both, toproduce a record of
11、the separation, or chromatogram, fromwhich detailed analysis can be obtained. The detector effluentmust be vented to a hood if the effluent contains toxicsubstances.4.2 Gas chromatography is essentially a physical separationtechnique. The separation is obtained when the sample mixturein the vapor ph
12、ase passes through a column containing astationary phase possessing special adsorptive properties. Thedegree of separation depends upon the differences in thedistribution of volatile compounds, organic or inorganic, be-tween a gaseous mobile phase and a selected stationary phasethat is contained in
13、a tube or GC column. In gas-liquidchromatography (GLC), the stationary phase is a nonvolatileliquid or gum coated as a thin film on a finely-divided, inert1This practice is under the jurisdiction of ASTM Committee E13 on MolecularSpectroscopy and is the direct responsibility of Subcommittee E13.19 o
14、n Chroma-tography.Current edition approved March 1, 2006. Published March 2006. Originallyapproved in 1965. Last previous edition approved in 2001 as E 260 96 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual B
15、ook of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Compressed Gas Association, Inc., 1725 Jefferson DavisHighway, Arlington, Suite 1004, VA 22202-4102.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
16、ocken, PA 19428-2959, United States.support of a relatively large surface area, and the distribution isbased on partition. The liquid phase should not react with, andshould have different partition coefficients for, the variouscomponents in the sample. In gas-solid chromatography(GSC), the stationar
17、y phase is a finely divided solid adsorbent(see 4.4).4.2.1 After separation in the analytical column, the compo-nents are detected, and the detector signal is related to theconcentration of the volatile components. Tentative identifica-tions can be made by comparison with the retention times ofknown
18、 standards under the same conditions, either on a singlecolumn or preferably by injecting the sample onto two columnsof different selectivity. Ancillary techniques, such as massspectrometry or infrared spectrophotometry, are generally nec-essary for positive identification of components in samples.4
19、.2.2 Prior to performing a GC analysis, the followingparameters must be considered:4.2.2.1 Sample preparation.4.2.2.2 Stationary phase and loading on support.4.2.2.3 Column material required.4.2.2.4 Solid support and mesh size.4.2.2.5 Column length and diameter.4.2.2.6 Instrument and detector type t
20、hat will be needed.4.2.2.7 Injector, column oven, and detector temperaturesrequired for analysis.4.2.2.8 Injection techniques, such as flash volatilization,on-column technique, purge and trap, pyrolysis, etc.4.2.2.9 Carrier gas and flow rate.4.2.2.10 Data handling and presentation.4.3 In gas-liquid
21、chromatography, the degree of separationpossible between any two compounds (solutes), is determinedby the ratio of their partition coefficients and the separationefficiency. The partition coefficient, K, is the ratio of the soluteconcentration in the liquid phase to the solute concentration inthe va
22、por phase at equilibrium conditions. The partition coef-ficient is affected by temperature and the chemical nature of thesolute (sample) and solvent (stationary phase).4.4 Another mechanism for separation is gas-solid chroma-tography. With this technique there is no liquid phase, only aporous polyme
23、r, molecular sieve, or solid adsorbent. Partitionis accomplished by distribution between the gas phase and thesolid phase.4.5 After the sample is resolved into individual componentsby the chromatographic column, the concentration or massflow of each component in the carrier gas can be measured byan
24、appropriate detector which sends an electrical signal to arecording potentiometer or other readout device. The curveobtained by plotting detector response against time is referredto as a chromatogram. For flame ionization and thermalconductivity detectors, either the peak areas or the peak heightsar
25、e proportional to the concentration of the components in thesample within the linear range of the detector system. How-ever, response fractors are not necessarily the same for allcompounds, and linearity of detector response may depend onoperating conditions. (Testing of detector performance isdiscu
26、ssed in ASTM Standard Practices for the appropriatedetector, see 2.1).4.6 Components in a mixture may be tentatively identifiedby retention time. Ideally, each substance has a unique reten-tion time in the chromatogram for a specific set of operatingconditions. However, caution is required because t
27、he GCseparation may be incomplete and a single peak may representmore than one compound. This is especially true of unknownmixtures and complex mixtures because of the very largenumber of possible compounds in existence and the finitenumber of peaks that a chromatograph might resolve. Addi-tional ch
28、aracterization data may be provided by ancillarytechniques, such as spectrometry.5. Significance and Use5.1 This practice describes a procedure for packed-columngas chromatography. It provides general comments, recom-mended techniques, and precautions.Arecommended form forreporting GC methods is giv
29、en in Section 14.6. Apparatus6.1 Carrier Gas SystemCommon carrier gases are heliumand nitrogen. Paragraph 7.6 provides more details on carriergases. Means must be provided to measure and control the flowrate of the carrier gas. Any flow or pressure control andmeasurement combination may be used that
30、 will give anaccurately known and reproducible flow rate over the desiredrange.6.1.1 The main gas supply is regulated with a two-stageregulator which must have a stainless steel diaphragm. Rubberor plastic diaphragms permit oxygen or water to diffuse into thecarrier gas. In addition, instruments wil
31、l have a flow controllerbetween the pressure regulator and column inlet to maintain aconstant flow during temperature programming. Copper orstainless steel carrier gas lines, not plastic tubing, should beused to avoid diffusion of oxygen (air) into the carrier gas.When using the thermal conductivity
32、 detector, variations in theFIG. 1 Block Diagram of a Basic Gas Chromatographic SystemE 260 96 (2006)2flow will change retention and response. The carrier gas linepressure must be higher than that required to maintain thecolumn flow at the upper temperature limit for the flowcontroller to operate pr
33、operly. A pressure of 40 to 60 psi isusually sufficient.6.2 Column Temperature ControlPrecise column tem-perature control is mandatory if reproducible analyses are to beobtained. Temperature control must be within 0.1C if reten-tion times are to be compared with another instrument.6.2.1 Air BathThe
34、thermostated forced-air bath is gener-ally accepted as the best practical method of temperatureregulation for most applications. Temperatures can be con-trolled by regulators or proportionally controlled heaters usinga thermocouple or platinum-resistance thermometer as a sens-ing element. The advant
35、age of a forced-air bath is the speed oftemperature equilibration. Air bath ovens are readily adaptableto temperature programming and are capable of operating overa range of 35 to 450C. This range can be extended downto 100C by using cryogenic equipment.6.2.2 Other DevicesLiquid baths, drying ovens,
36、 incuba-tors, or vapor jacket enclosures are less stable, less convenientmeans of providing a source of heat to maintain or raise thetemperature of a chromatographic column. These devices arenot recommended for precision chromatographic applications.6.3 The Injection PortThe purpose of the injection
37、 port isto introduce the sample into the gas chromatographic columnby instantaneous volatilization following injection into the gaschromatographic system. Two sample inlet types are in com-mon use in gas chromatography: the flash vaporization and theon-column injection inlets.6.3.1 The temperature o
38、f the flash vaporization inlet shouldbe above the boiling points of the sample components and islimited by the amount of septum bleed generated and thetemperature stability of sample components. It should be set atthat temperature above which no improvement in peak shapeoccurs but should be determin
39、ed by the nature of the sampleand the volume injected, not by the temperature of the column.If the inlet temperature is too low, broad peak with a slowlyrising front edge will result from slow vaporization of thesample. If the temperature is set far above what is necessary toproduce fast vaporizatio
40、n, thermal decomposition of thesample, decreased septum life, and ghost peaks due to septumbleed may be observed. Generally, a good guideline is tomaintain the inlet temperature 25 to 30C higher than thehighest boiling point of any sample component.6.3.2 A glass liner placed inside the injection por
41、t willeliminate sample contact with hot metal inner walls of the inlet,which can catalyze thermal decompositions. Any debris left inthe liner, especially from biological samples, can be a source ofexcessive sample adsorption. If a liner is used, the debris caneasily be removed by replacing the liner
42、. Deactivation of theglass liner by treatment with dimethyldichlorosilane may benecessary for some compounds.6.3.3 With on-column injection technique, the sample isdeposited in the liquid state directly on the column packing.The sample must be small enough to preclude flooding of thecolumn, with pos
43、sible detrimental effects to peak shape andcolumn life. Ideally, the on-column inlet is a part of thecolumn, so its temperature may be controlled as the columntemperature is controlled. In practice, because an on-columninlet usually has a somewhat higher thermal mass than anequivalent sector of the
44、rest of the column, the inlet must beheated somewhat above the maximum analysis temperature ofthe column oven. The criteria of good peak shape andquantitation should be used to determine the maximum re-quired temperature for the inlet. One should consider thetemperature limit of the column packing w
45、hen heating theinjection inlet and detector. With some samples, a nonheatedinjection port is adequate, especially with temperature-programmed operation.6.3.4 Injection Port Septum:6.3.4.1 The septum is a disc, usually made of siliconerubber, which seals one end of the injection port. It is important
46、to change the septum frequently after two to three dozeninjections, or preferably at the end of the working day. The besttechnique is to change the septum when the column isrelatively cool (below 50C) to avoid contact of stationaryphase in a hot column with air (danger of oxidation). After theseptum
47、 is changed, return the inlet temperature to that whichwas originally set. The inlet temperature should be the opti-mum for the particular analysis, as well as within the recom-mended operating temperature of the septum. If the septum ispunctured too many times, it will leak air into the gaschromato
48、graphic system, even though it is under pressure. Athigh temperatures, above 150 to 200C, air (oxygen) in thecarrier gas from a septum leak will degrade the stationaryphase. An excessive septum leak will also produce a change incarrier gas flow rate (a change in retention time) and loss ofsample (ir
49、reproducible peak heights) due to outflow from theleak. When installing the septum, do not overtighten theretaining nut. The septa will swell at high temperature andextrude out of the injection port.Asnug fit at room temperatureis sufficient. It is important for septum life to make sure theinjection needle is sharp with no bent tip. Fine emery cloth, ora fine sharpening stone, can be used to sharpen the point.6.3.4.2 Ghost peaks may be observed in temperature pro-grammed runs due to septum bleed. Septum bleed is due to thethermal decomposition, 300C or higher, of the s
