1、Designation: D7266 131Standard 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 revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEThe number of samples in Section 15.1 was corrected editorially in April 2013.1. Scope*1.1 This test method covers the determi
3、nation of 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 f
4、ound in cyclohexane. 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 berou
5、nded off 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
6、is theresponsibility of the user 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:2D3437 Practice for Sampling and Han
7、dling 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 Ma-terialsE29 Practice for Usi
8、ng 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 Silica Open TubularCapillary
9、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 chromatograph(GC) equipped with a flame
10、 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 anexternal standard methodology. Purity by GC (the cyclohexanecontent) is calculated by subtra
11、cting 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 onthe materials referenced in Table 1 and for use as an internal1This test m
12、ethod 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 Feb. 1, 2013. Published March 2013. Originallyapproved in
13、 2007. Last previous edition approved in 2007 as D7266 071. DOI:10.1520/D7266-13E01.2For 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 p
14、age onthe ASTM website.3Available 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Dri
15、ve, PO Box C700, West Conshohocken, PA 19428-2959. United States1quality 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 wi
16、th 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 op
17、erated 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 cap
18、able 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
19、 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 conf
20、orm 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
21、 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.
22、Purify 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 MaterialSafety Data Sheets, and local regulations for all materials listedin this test method.9. Sampling and Handling9
23、.1 Sample the material in accordance with Practice D3437.10. 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 allowing4Reagent Chemicals, American Chemical
24、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. Pharmac
25、opeial 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(12)
26、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-dimethylcyclopentane
27、(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 ionizatio
28、nInjection 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/mi
29、n to200C, hold for 5 minCarrier gas HydrogenFlow rate, mls/min 3Split ratio 100:1Sample size, l 1.0 Corrected editorially.D7266 1312FIG. 1 Typical Chromatogram of Calibration Mixture Using Conditions in Table 2D7266 1313sufficient time for the equipment to reach equilibrium. SeePractices E1510 and E
30、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 withPractice D4307. The weight o
31、f 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 andmethylcyclopentane, as well as for a number of
32、 the otherimpurities listed 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 Determine the response factor for each
33、 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 calculate an average Rfi. Subseque
34、nt 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 factor for n-hexane is used for unkno
35、wns.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 impurity as fol-lows:Ci5 Ai!Rfi
36、! (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(Ci10000(3)where:Ct= total concentration of all impurities in wt %.13.3 Calculate the purity of cyc
37、lohexane as follows:Cyclohexane, weight percent 5 100.00 2 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 Bias515.1 An ILS was conducted which included two laborato-ries analyzing six samples t
38、hree times. One lab analyzed thesamples on two different instruments. Practice E691 wasfollowed for the design and 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:D16-104
39、5.15.2 Repeatability (r)Results should not be suspect unlessthey differ by more than shown in Tables 3-7. Results 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 sh
40、own in Tables 3-7. Results differing by less than “R”have a 95 % probability of being correct.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1045. ContactASTM CustomerService at serviceastm.org.TABLE 3 Methylcyclopentane (m
41、g/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 laboratories calculated averages.D7266 131415.4 BiasSince there is no accepted reference materialsuitable for determining the bi
42、as 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 added to the samples:Sample 1mg/kgSample 2mg/kgSample 3mg/kgSamp
43、le 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.16.1.1 Confirm the performance of the test instrument ortest method
44、 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 analyzed.16.1.3 When QA/QC protocols are already established
45、 inthe testing facility, these protocols are acceptable when theyconfirm the validity of test results.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 ca
46、lculated averages.TABLE 5 Methylcyclohexane (mg/kg)AverageARepeatabilityLimitReproducibilityLimitXrRBlank 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)AverageARepeatabilityLimitR
47、eproducibilityLimitXrRBlank 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.TABLE 7 Cyclohexane (wt %)AverageARepeatabilityLimitReproducibilityLimitXrRBlank 99.948 0.003 0.030Sample 1 99.895 0.005 0.
48、066Sample 2 99.905 0.003 0.058Sample 3 99.921 0.002 0.047Sample 4 99.935 0.002 0.040Sample 5 99.945 0.001 0.030AThe average of the laboratories calculated averages.D7266 131516.1.4 When there are no QA/QC protocols established inthe testing facility, use the guidelines described in GuideD6809 or sim
49、ilar statistical quality control practices.17. Keywords17.1 analysis by gas chromatography; benzene; cyclo-hexaneSUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard since the last issue (D7266 071) that may impact the use of this standard. (Approved February 1, 2013.)(1) The scope was expanded to determine impurities from 3 to200 mg/kg.(2) Precision and Bias was replaced with a complete precisionstatement.(3) Quality Guidelines was replaced with the current editorialguidelines for quali
