1、Designation: D 7266 071Standard Test Method forAnalysis of Cyclohexane by Gas Chromatography (ExternalStandard)1This standard is issued under the fixed designation D 7266; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTETable 2 was corrected editorially in July 2008.1. Scope1.1 This test method covers the determination of the purityof cyclohe
3、xane by gas chromatography. Calibration of the gaschromatography system is done by the external standardcalibration technique.1.2 This test method has been found applicable to themeasurement of impurities such as those found in Table 1,which are impurities that may be found in cyclohexane. Theimpuri
4、ties can be analyzed over a range of 5 to 180 mg/kg bythis method, but may be applicable to a wider range.1.3 The limit of detection is 1 mg/kg.1.4 In determining the conformance of the test results usingthis test method to applicable specifications, results shall berounded off in accordance with th
5、e rounding-off method ofPractice E29.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the us
6、er of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D 3437 Practice for Sampling and Handling Liquid CyclicProductsD
7、4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4790 Terminology of Aromatic Hydrocarbons and Re-lated ChemicalsD 6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in
8、 Test Data toDetermine Conformance with SpecificationsE 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR, paragraphs 1910.1000 and1910.120033. Termino
9、logy3.1 See Terminology D 4790 for definitions of terms used inthis test method.4. Summary of Test Method4.1 Cyclohexane is analyzed using a gas chromatograph(GC) equipped with a flame ionization detector (FID). Aprecisely repeatable volume of the sample to be analyzed isinjected onto the gas chroma
10、tograph. The peak areas of theimpurities are measured and converted to concentrations via anexternal standard methodology. Purity by GC (the cyclohexanecontent) is calculated by subtracting the sum of the impuritiesfrom 100.00. Individual impurities are reported in mg/kg. Thecyclohexane purity is re
11、ported in weight percent.5. Significance and Use5.1 This test method is suitable for setting specifications onthe materials referenced in Table 1 and for use as an internalquality control tool where cyclohexane is produced or is usedin a manufacturing process. It may also be used in developmentor re
12、search work involving cyclohexane.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.01 on Benzene, Toluene, Xylenes, Cyclohexane and TheirDerivatives.Current edition approved Jan. 1, 200
13、7. Published January 2007.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from U.S. Government Pri
14、nting Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 This test method is useful in determining the purity
15、ofcyclohexane with normal impurities present. If extremely highboiling or unusual impurities are present in the cyclohexane,this test method would not necessarily detect them and thepurity calculation would be erroneous.6. Apparatus6.1 Gas ChromatographAny instrument having a flameionization detecto
16、r that can be operated at the conditions givenin Table 2. The system should have sufficient sensitivity toobtain a minimum peak height response for 1 mg/kg benzeneof twice the height of the signal background noise.6.2 ColumnsThe choice of column is based on resolutionrequirements. Any column may be
17、used that is capable ofresolving all significant impurities from cyclohexane. Thecolumn described in Table 2 has been used successfully.6.3 RecorderElectronic integration is required.6.4 InjectorThe specimen must be precisely and repeat-ably injected into the gas chromatograph.An automatic sampleinj
18、ection device is highly recommended. Manual injection canbe employed if the precision stated in Table 3 can be reliablyand consistently satisfied.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reage
19、nts shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening thea
20、ccuracy of the determination.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and
21、 the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Impurities Known or Suggested to be Present inCommercial CyclohexaneC4(1) n-butane(2) isobuteneC5(3) n-pentaneA(4) isopentaneA(5) cyclopentaneAC6(6) n-hexane(7) 2-methylpentaneA(8)
22、 3-methylpentaneA(9) methylcyclopentaneA(10) benzeneA(11) cyclohexeneA(12) 2,2-dimethylbutaneA(13) 2,3-dimethylbutaneAC7(14) 3,3-dimethylpentane(15) 2,2-dimethylpentaneA(16) 2,3-dimethylpentaneA(17) 2,4-dimethylpentaneA(18) 1,1-dimethylcyclopentaneA(19) trans-1,3-dimethylcyclopentaneA(20) trans-1,2-
23、dimethylcyclopentaneA(21) cis-1,2-dimethylcyclopentane(22) 2,2-dimethylcyclopentane(23) 2,4-dimethylcyclopentane(24) cis-1,3-dimethylcyclopentaneA(25) ethylcyclopentaneA(26) methylcyclohexaneA(27) 3-ethylpentaneA(28) 3-methylhexaneA(29) 2-methylhexaneA(30) n-heptaneA(31) tolueneAC8(32) iso-octaneA(3
24、3) p-xyleneAC9(34) isopropylcylohexaneAAThese components were used to prepare the standard used in the repeatabil-ity program.TABLE 2 Instrumental ParametersDetector flame ionizationInjection Port capillary splitterColumn A:Tubing fused silicaStationary phase bonded and crosslinked 100 % dimethylpol
25、ysiloxaneFilm thickness, m 0.5Length, m 100Diameter, mm 0.25Temperatures:Injector, C 230Detector, C 250Oven, C 32 hold for 12 minRamp 1 = 8C/min to 64C, hold for 10 minRamp 2 = 10C/min to 200C, hold for 5 minCarrier gas HydrogenFlow rate, mls/min 3Split ratio 100:1Sample size, l 1.0 Corrected editor
26、ially.TABLE 3 Summary of Precision Data (mg/kg)ImpurityExpectedValueAverage RepeatabilityIsopentane 21.1 21.1 2.0n-pentane 24.7 25.8 3.02,2-dimethylbutane 9.9 9.9 1.0cyclopentane 11.5 11.4 0.82,3-diemthylbutane 10.0 10.2 1.02-methylpentane 17.3 18.1 2.23-methylpentane 23.9 24.8 2.0n-hexane 46.7 48.4
27、 5.22,2-dimethylpentane 4.9 5.2 0.8methycylopentane 36.1 36.8 2.12,4-dimethylpentane 49.7 51.7 5.1benzene 12.1 12.4 1.32,3-dimethylpentane 57.3 58.3 4.21,1-dimethylcyclopentane 23.5 23.0 1.2cyclohexene 29.4 29.6 1.33-methylhexane 9.9 10.5 0.9cis-1,3-dimethylcyclopentane 22.6 23.6 1.6trans-1,3-dimeth
28、ylcyclopentane 10.8 11.1 0.83-ethylpentane 29.9 31.0 2.5trans-1,2-dimethylcyclopentane 41.2 40.4 2.3isooctane 10.0 10.5 1.1n-heptane 37.1 38.4 3.7methylcyclohexane 178.5 181.0 10.0ethylcyclopentane 19.0 19.6 1.7toluene 19.9 20.9 1.9para-xylene 19.9 20.9 2.0isopropylcyclohexane 19.6 20.4 1.8D72660712
29、7.2 GasesHelium, hydrogen, nitrogen, or other as carrier.Carrier, makeup, and detector gases (except air) 99.999 %minimum purity. Oxygen in carrier gas less than 1 ppm, lessthan 0.5 ppm is preferred. Purify carrier, makeup, and detectorgases to remove oxygen, water, and hydrocarbons. Purify air tore
30、move hydrocarbons and water, and the air used for an FIDshould contain less than 0.1 ppm total hydrocarbons.8. Hazards8.1 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets, and local regulations for all materials listedin this test method.9. Sampling and Handling9.1 Sample the m
31、aterial in accordance with PracticeD 3437.10. Preparation of Apparatus10.1 Follow manufacturers instructions for mounting andconditioning the column into the chromatograph and adjustingthe instrument to the conditions described in Table 2 allowingsufficient time for the equipment to reach equilibriu
32、m. SeePractices E 1510 and E 355 for additional information on gaschromatography practices and terminology.11. Calibration11.1 Prepare a synthetic mixture of high purity cyclohexanecontaining impurities at concentrations representative of thoseexpected in the samples to be analyzed in accordance wit
33、hPractice D 4307. The weight of each hydrocarbon impuritymust be measured to the nearest 0.1 mg. Because the avail-ability of stock cyclohexane with a purity higher than 99.97 %is problematic, the method of standard additions may berequired for impurities such as methycyclohexane and meth-ylcyclopen
34、tane, as well as for a number of the other impuritieslisted in Table 1 that are commonly present.11.2 Inject the resulting solution from 11.1 into the gaschromatograph, collect and process the data. A typical chro-matogram is illustrated in Fig. 1 based on the conditions listedin Table 2.11.3 Determ
35、ine the response factor for each impurity in thecalibration mixture as follows:Rfi5CiAi(1)where:Rfi= response factor for impurity i,Ci= concentration of impurity i in the calibration mixture,andAi= peak area of impurity i.11.4 Initially analyze the calibration solution a minimum ofthree times and ca
36、lculate an average Rfi. Subsequent calibra-tions may be a single analysis as long as the response factorsfor all components of interest are within 65 % of the initialvalidation response factors. A “rolling” average as defined bymost modern chromatographic software may also be used. Theresponse facto
37、r for n-hexane is used for unknowns.12. Procedure12.1 Inject into the gas chromatograph an appropriateamount of sample as previously determined in accordance with6.1 and start the analysis.12.2 Obtain a chromatogram and peak integration report.13. Calculations13.1 Calculate the concentration of each
38、 impurity as fol-lows:Ci5 Ai! Rfi! (2)where:Ci= concentration of component i in mg/kg,Ai= peak area of component i, andRfi= response factor for component i.13.2 Calculate the total concentration of all impurities in wt% as follows:Ct5(Ci10 000(3)where:Ct= total concentration of all impurities in wt
39、%.13.3 Calculate the purity of cyclohexane as follows:Cyclohexane, weight percent 5 100.00 Ct(4)14. Report14.1 Report the individual impurities to the nearest mg/kg.14.2 Report the purity of cyclohexane to the nearest 0.01 wt%.15. Precision and Bias15.1 RepeatabilityResults within the same laborator
40、y bythe same operator with the same equipment over the shortestpractical period of time should not be considered suspectunless they differ by more than the amounts shown in Table 3.A single sample was analyzed 20 times over the shortestpractical time.15.2 ReproducibilityReproducibility has not been
41、deter-mined at this time.15.3 BiasThe bias of the test method has not beendetermined since there is not an accepted reference material tomake the determination.16. Quality Guidelines16.1 Refer to Guide D 6809 for suggested QA/QC activitiesthat can be used as a part of this test method. It is recom-m
42、ended that the operator of this test method select and performrelevant QA/QC activities like the ones in Guide D 6809 tohelp ensure the quality of data generated by this test method.17. Keywords17.1 analysis by gas chromatography; benzene;cyclohexaneD72660713FIG. 1 Typical Chromatogram of Calibratio
43、n Mixture Using Conditions in Table 2D72660714ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, a
44、nd the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revis
45、ion of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you s
46、houldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D72660715
