1、Designation: D 7266 07Standard 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the purityof cyclohexane by gas chromatography. Calibration of the gasch
3、romatography 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. Theimpurities can be analyzed over a range of 5 to 180 mg/kg
4、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 the rounding-off method ofPractice E29.1.5 The values
5、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 user of this standard to establish appro-priate safety
6、 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 4307 Practice for Preparation of Liquid Blends for U
7、se 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 Test Data toDetermine Conformance with Specificatio
8、nsE 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. Terminology3.1 See Terminology D 4790 for definitions of te
9、rms 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 chromatograph. The peak areas of theimpurities are measure
10、d 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 reported in weight percent.5. Significance and Use5.1
11、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 research work involving cyclohexane.5.2 This test meth
12、od is useful in determining the purity 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.1This test method is under the jurisdicti
13、on 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, 2007. Published January 2007.2For referenced ASTM standards, visit the ASTM we
14、bsite, 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 Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop:
15、 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.6. Apparatus6.1 Gas ChromatographAny instrument having a flameionization detector that can be operated at the conditions givenin Tab
16、le 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 used that is capable ofresolving all significant imp
17、urities 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 sampleinjection device is highly recommended. Manual injectio
18、n 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 reagents shall conform to the specifications of the Commi
19、t-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 theaccuracy of the determination.7.2 GasesHelium, hydrog
20、en, 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 to4Reagent Chemicals, Ameri
21、can 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 the United States Pharmacopeiaand National Formulary
22、, 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) 3-methylpentaneA(9) methylcyclopentaneA(10) benzeneA
23、(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-dimethylcyclopentaneA(21) cis-1,2-dimethylcyclopentan
24、e(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(33) p-xyleneAC9(34) isopropylcylohexaneAAThese compone
25、nts 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% dimethylpolysilicaneFilm thickness, m 0.5Length, m 100Diameter, m
26、m 0.25Temperatures:Injector, C 230Detector, C 250Oven, C 32 hold for 12 minRamp1=8C/minto64C, hold for 10 minRamp 2 = 10C/min to 200C, hold for 5 minCarrier gas HydrogenFlow rate, mls/min 3Split ratio 100:1Sample size, l 1.0TABLE 3 Summary of Precision Data (mg/kg)ImpurityExpectedValueAverage Repeat
27、abilityIsopentane 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 5.22,2-dimethylpentane 4.9 5.2 0.8methycylopentane 36.1 36.8 2.12,4-dimethylpenta
28、ne 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-dimethylcyclopentane 10.8 11.1 0.83-ethylpentane 29.9 31.0 2.5trans-1,2-dimethylcyclopen
29、tane 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 1.8D7266072remove hydrocarbons and water, and the air used for an FIDshould contain less than
30、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 material in accordance with PracticeD 3437.10. Preparation of Apparatus10.1 Follow
31、 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 equilibrium. SeePractices E 1510 and E 355 for additional information on gaschromatography
32、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 withPractice D 4307. The weight of each hydrocarbon impuritymust be measured to the
33、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-ylcyclopentane, as well as for a number of the other impuritieslisted in Table 1 that are c
34、ommonly 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 Determine the response factor for each impurity in thecalibration mixture as follows:Rf
35、i5CiAi(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 calculate an average Rfi. Subsequent calibra-tions may be a single analysis as long
36、 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 factor for n-hexane is used for unknowns.12. Procedure12.1 Inject into the gas chromat
37、ograph 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 impurity as fol-lows:Ci5 Ai! Rfi! (2)where:Ci= concentration of component i in m
38、g/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 %.13.3 Calculate the purity of cyclohexane as follows:Cyclohexane, weight percent
39、 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 laboratory bythe same operator with the same equipment over the shortestpractical period o
40、f 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 deter-mined at this time.15.3 BiasThe bias of the test method has not beendetermi
41、ned 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-mended that the operator of this test method select and performrelevant QA/QC acti
42、vities 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;cyclohexaneD7266073FIG. 1 Typical Chromatogram of Calibration Mixture Using Conditions in Table 2D7266074ASTM International takes no position
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45、ernational 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 shouldmake your views known to the ASTM Committee on Standards, at the address shown
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