1、Designation: D7266 13 (Reapproved 2018)1Standard Test Method forAnalysis of Cyclohexane by Gas Chromatography (ExternalStandard)1This standard is issued under the fixed designation D7266; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTESection 8 was editorially corrected in January 2018.1. Scope1.1 This test method covers the determination of
3、 the purityof cyclohexane 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 c
4、yclohexane. Theimpurities can be analyzed over a range of 3 to 200 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
5、in accordance with the 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 theres
6、ponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.For specific hazard statements, see Section 8.1.7 This international standard was developed in accor-dance with inter
7、nationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D3437
8、 Practice for Sampling and Handling Liquid CyclicProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related
9、Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE355 Practice for Gas Chromatography Terms and Relation-shipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1510 Practice for Installing Fused
10、 Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120033. Terminology3.1 See Terminology D4790 for definitions of terms used inthis test method.4. Summary of Test Method4.1 Cyclohexane is analyzed using a gas chromatog
11、raph(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 measured and converted to concentrations via an1This test method is under the jurisdiction of ASTM Committee
12、D16 onAromatic, Industrial, Specialty and Related Chemicals and is the direct responsi-bility of Subcommittee D16.01 on Benzene, Toluene, Xylenes, Cyclohexane andTheir Derivatives.Current edition approved Jan. 1, 2018. Published January 2018. Originallyapproved in 2007. Last previous edition approve
13、d in 2013 as D7266 131. DOI:10.1520/D7266-13R18E01.2For 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
14、 from U.S. Government Printing Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was de
15、veloped in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1external standar
16、d 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 This test method is suitable for setting specifications
17、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 method is useful in determining the purity ofcyclohexane wit
18、h 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 detector that can be ope
19、rated 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 used that is capa
20、ble 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 sampleinjection device is
21、highly recommended. Manual injection canbe employed if the precision stated in Tables 37 can bereliably and 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 confo
22、rm 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 theaccuracy of the
23、determination.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. P
24、urify air toremove 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 SafetyData Sheets, and local regulations for all materials listed in thistest method.4Reagent Chemicals, American Chemic
25、al 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, U.S. Phar
26、macopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Impurities Known or Suggested to be Present inCommercial CyclohexaneC4(1) n-butane(2) isobuteneC5(3) n-pentane(4) isopentane(5) cyclopentaneC6(6) n-hexane(7) 2-methylpentane(8) 3-methylpentane(9) methylcyclopentane(10) benzene(11) cyclohexene(1
27、2) 2,2-dimethylbutane(13) 2,3-dimethylbutaneC7(14) 3,3-dimethylpentane(15) 2,2-dimethylpentane(16) 2,3-dimethylpentane(17) 2,4-dimethylpentane(18) 1,1-dimethylcyclopentane(19) trans-1,3-dimethylcyclopentane(20) trans-1,2-dimethylcyclopentane(21) cis-1,2-dimethylcyclopentane(22) 2,2-dimethylcyclopent
28、ane(23) 2,4-dimethylcyclopentane(24) cis-1,3-dimethylcyclopentane(25) ethylcyclopentane(26) methylcyclohexane(27) 3-ethylpentane(28) 3-methylhexane(29) 2-methylhexane(30) n-heptane(31) tolueneC8(32) iso-octane(33) p-xyleneC9(34) isopropylcylohexaneTABLE 2 Instrumental ParametersDetector flame ioniza
29、tionInjection Port capillary splitterColumn A:Tubing fused silicaStationary phase bonded and crosslinked100 % dimethylpolysiloxaneFilm 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
30、/min to200C, hold for 5 minCarrier gas HydrogenFlow rate, mls/min 3Split ratio 100:1Sample size, l 1.0D7266 13 (2018)129. Sampling and Handling9.1 Sample the material in accordance with Practice D3437.10. Preparation of Apparatus10.1 Follow manufacturers instructions for mounting andconditioning the
31、 column into the chromatograph and adjustingthe instrument to the conditions described in Table 2 allowingsufficient time for the equipment to reach equilibrium. SeePractices E1510 and E355 for additional information on gaschromatography practices and terminology.11. Calibration11.1 Prepare a synthe
32、tic mixture of high purity cyclohexanecontaining impurities at concentrations representative of thoseexpected in the samples to be analyzed in accordance withPractice D4307. The weight of each hydrocarbon impuritymust be measured to the nearest 0.1 mg. Because the avail-ability of stock cyclohexane
33、with a purity higher than 99.97 %is problematic, the method of standard additions may berequired for impurities such as methycyclohexane andmethylcyclopentane, as well as for a number of the otherimpurities listed in Table 1 that are commonly present.11.2 Inject the resulting solution from 11.1 into
34、 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:Rfi5CiAi(1)where:Rfi= response factor for impurity i,Ci= concentrat
35、ion 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 as the response factorsfor all components of interest are within
36、 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 chromatograph an appropriateamount of sample as previously determined in
37、 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 mg/kg,Ai= peak area of component i, andRfi= response factor for com
38、ponent i.13.2 Calculate the total concentration of all impurities in wt% as follows:Ct5(Ci10000(3)where:Ct= total concentration of all impurities in wt %.13.3 Calculate the purity of cyclohexane as follows:Cyclohexane, weight percent 5 100.00 2 Ct(4)14. Report14.1 Report the individual impurities to
39、 the nearest mg/kg.14.2 Report the purity of cyclohexane to the nearest 0.01 wt%.15. Precision and Bias515.1 An ILS was conducted which included two laborato-ries analyzing six samples three times. One lab analyzed thesamples on two different instruments. Practice E691 wasfollowed for the design and
40、 analysis of the data; this ILS didnot meet Practice E691 minimum requirements of six labs, fourmaterials, and two replicates. The details are given in ASTMResearch Report No. RR:D16-1045.15.2 Repeatability (r)Results should not be suspect unlessthey differ by more than shown in Tables 3-7. Results
41、differingby less than “r” have a 95 % probability of being correct.15.3 Reproducibility (R)Results submitted by two labsshould not be considered suspect unless they differ by morethan shown in Tables 3-7. Results differing by less than “R”have a 95 % probability of being correct.15.4 BiasSince there
42、 is no accepted reference materialsuitable for determining the bias in this test method, bias hasnot been determined.15.5 The precision statement was determined through sta-tistical examination of 270 results, from two laboratories, on ablank and five samples. The following amounts of impuritieswere
43、 added to the samples:Sample 1mg/kgSample 2mg/kgSample 3mg/kgSample 4mg/kgSample 5mg/kghexane 199 159 100 50 10methylcyclopentane 150 119.9 75 37.5 7.5benzene 49.9 39.9 25 12.5 2.5methycyclohexane 201 160 100 50 1016. Quality Guidelines16.1 Laboratories shall have a quality control system inplace.5S
44、upporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1045. ContactASTM CustomerService at serviceastm.org.D7266 13 (2018)13FIG. 1 Typical Chromatogram of Calibration Mixture Using Conditions in Table 2D7266 13 (2018)1416.1.1 Confir
45、m the performance of the test instrument ortest method by analyzing a quality control sample followingthe guidelines of standard statistical quality control practices.16.1.2 A quality control sample is a stable material isolatedfrom the production process and representative of the samplebeing analyz
46、ed.16.1.3 When QA/QC protocols are already established inthe testing facility, these protocols are acceptable when theyconfirm the validity of test results.16.1.4 When there are no QA/QC protocols established inthe testing facility, use the guidelines described in GuideD6809 or similar statistical q
47、uality control practices.17. Keywords17.1 analysis by gas chromatography; benzene;cyclohexaneTABLE 3 Methylcyclopentane (mg/kg)AverageARepeatabilityLimitReproducibilityLimitXrRBlank 93 4 12Sample 1 249 7 24Sample 2 217 4 28Sample 3 170 3 22Sample 4 131 3 13Sample 5 101 2 14AThe average of the labora
48、tories calculated averages.TABLE 4 Benzene (mg/kg)AverageARepeatabilityLimitReproducibilityLimitXrRBlank 0 0 0Sample 1 43 1 39Sample 2 34 1 30Sample 3 22 1 19Sample 4 11 0.4 10Sample 5 3 1 3AThe average of the laboratories calculated averages.TABLE 5 Methylcyclohexane (mg/kg)AverageARepeatabilityLim
49、itReproducibilityLimitXrRBlank 75 3 23Sample 1 264 7 89Sample 2 227 5 74Sample 3 172 4 60Sample 4 124 3 44Sample 5 88 15 36AThe average of the laboratories calculated averages.TABLE 6 Hexane (mg/kg)AverageARepeatabilityLimitReproducibilityLimitXrRBlank 212 10 10Sample 1 410 10 19Sample 2 369 11 23Sample 3 307 6 21Sample 4 258 7 11Sample 5 220 3 12AThe average of the laboratories calculated averages.D7266 13 (2018)15ASTM International takes no position respecting the validity of any patent rights asserted in conn
