1、Designation: D7266 071D7266 13Standard 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 y
2、ear 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.1 NOTETable 2 was corrected editorially in July 2008.1. Scope Scope*1.1 This test method covers the determination of the pu
3、rity of cyclohexane by gas chromatography. Calibration of the gaschromatography system is done by the external standard calibration technique.1.2 This test method has been found applicable to the measurement of impurities such as those found in Table 1, which areimpurities that may be found in cyclo
4、hexane. The impurities can be analyzed over a range of 53 to 180200 mg/kg by this 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 using this test method to applicable specifications, results shall be roundedof
5、f in accordance with the rounding-off method of Practice E29.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is
6、the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For specific hazard statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D3437 Practice for Sampling and Handling
7、 Liquid Cyclic ProductsD4307 Practice for Preparation of Liquid Blends for Use as Analytical StandardsD4790 Terminology of Aromatic Hydrocarbons and Related ChemicalsD6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE29 Practice for Using
8、 Significant Digits in Test Data to Determine Conformance with SpecificationsE355 Practice for Gas Chromatography Terms and RelationshipsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE1510 Practice for Installing Fused Silica Open Tubular Capillary
9、Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR,CFR paragraphs 1910.1000 and 1910.1200 33. Terminology3.1 See Terminology D4790 for definitions of terms used in this test method.4. Summary of Test Method4.1 Cyclohexane is analyzed using a gas chromatograph (GC) equipped with
10、 a flame ionization detector (FID). A preciselyrepeatable volume of the sample to be analyzed is injected onto the gas chromatograph. The peak areas of the impurities are1 This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons and Related Chemicals and is the direc
11、t responsibility of SubcommitteeD16.01 on Benzene, Toluene, Xylenes, Cyclohexane and Their Derivatives.Current edition approved Jan. 1, 2007Feb. 1, 2013. Published January 2007March 2013. Originally approved in 2007. Last previous edition approved in 2007 as D7266 071. DOI: 10.1520/D7266-07E01.10.15
12、20/D7266-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from U.S. Government Printing Office
13、Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may n
14、ot be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the e
15、nd of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1measured and converted to concentrations via an external standard methodology. Purity by GC (the cyclohexane content) iscalculated by subtracting the sum of the impuri
16、ties from 100.00. Individual impurities are reported in mg/kg. The cyclohexanepurity is reported in weight percent.5. Significance and Use5.1 This test method is suitable for setting specifications on the materials referenced in Table 1 and for use as an internal qualitycontrol tool where cyclohexan
17、e is produced or is used in a manufacturing process. It may also be used in development or researchwork involving cyclohexane.5.2 This test method is useful in determining the purity of cyclohexane with normal impurities present. If extremely high boilingor unusual impurities are present in the cycl
18、ohexane, this test method would not necessarily detect them and the purity calculationwould be erroneous.6. Apparatus6.1 Gas ChromatographAny instrument having a flame ionization detector that can be operated at the conditions given inTable 2. The system should have sufficient sensitivity to obtain
19、a minimum peak height response for 1 mg/kg benzene of twicethe height of the signal background noise.6.2 ColumnsThe choice of column is based on resolution requirements.Any column may be used that is capable of resolvingall significant impurities from cyclohexane. The column described in Table 2 has
20、 been used successfully.6.3 RecorderElectronic integration is required.6.4 InjectorThe specimen must be precisely and repeatably injected into the gas chromatograph. An automatic sampleinjection device is highly recommended. Manual injection can be employed if the precision stated in Table 3Tables 3
21、7 can bereliably and consistently satisfied.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemi
22、cal Society, wheresuch specifications are available.4 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.7.2 GasesHelium, hydrogen, nitrogen, or other as carrier. Carrier, mak
23、eup, and detector gases (except air) 99.999 % minimumpurity. Oxygen in carrier gas less than 1 ppm, less than 0.5 ppm is preferred. Purify carrier, makeup, and detector gases to removeoxygen, water, and hydrocarbons. Purify air to remove hydrocarbons and water, and the air used for an FID should con
24、tain lessthan 0.1 ppm total hydrocarbons.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Do
25、rset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.TABLE 2 Instrumental ParametersDetector flame ionizationInjection Port capillary splitterColumn A:Tubing fused silicaStationary phase bonded and crosslinked100 % dimethylpo
26、lysiloxaneFilm 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 to200C, hold for 5 minCarrier gas HydrogenFlow rate, mls/min 3Split ratio 100:1Sample size, l 1.0A These components
27、 were used to prepare the standard used in the repeatabilityprogram.D7266 1328. Hazards8.1 Consult current OSHA regulations, suppliers Material Safety Data Sheets, and local regulations for all materials listed inthis test method.9. Sampling and Handling9.1 Sample the material in accordance with Pra
28、ctice D3437.10. Preparation of Apparatus10.1 Follow manufacturers instructions for mounting and conditioning the column into the chromatograph and adjusting theinstrument to the conditions described in Table 2 allowing sufficient time for the equipment to reach equilibrium. See PracticesE1510 and E3
29、55 for additional information on gas chromatography practices and terminology.11. Calibration11.1 Prepare a synthetic mixture of high purity cyclohexane containing impurities at concentrations representative of thoseexpected in the samples to be analyzed in accordance with Practice D4307. The weight
30、 of each hydrocarbon impurity must bemeasured to the nearest 0.1 mg. Because the availability of stock cyclohexane with a purity higher than 99.97 % is problematic,the method of standard additions may be required for impurities such as methycyclohexane and methylcyclopentane, as well asfor a number
31、of the other impurities listed in Table 1 that are commonly present.11.2 Inject the resulting solution from 11.1 into the gas chromatograph, collect and process the data. A typical chromatogramis illustrated in Fig. 1 based on the conditions listed in Table 2.TABLE 3 Summary of Precision Data (mg/kg
32、)align=“center“ colwidth=“1.5in“ align=“center“colwidth=“0.43in“Impurity ExpectedValue Average 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.
33、0n-hexane 46.7 48.4 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-dimethylcyclopentane23.5 23.0 1.2cyclohexene 29.4 29.6 1.33-methylhexane 9.9 10.5 0.9cis-1,3-dimethylcyclopentane22.6 23.6 1.
34、6trans-1,3-dimethylcyclopentane10.8 11.1 0.83-ethylpentane 29.9 31.0 2.5trans-1,2-dimethylcyclopentane41.2 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
35、.4 1.8TABLE 3 Methylcyclopentane (mg/kg)AverageARepeatabilityLimitReproducibilityLimitX r RBlank 93 4 12Sample 1 249 7 24Sample 2 217 4 28Sample 3 170 3 22Sample 4 131 3 13Sample 5 101 2 14A The average of the laboratories calculated averages.D7266 133FIG. 1 Typical Chromatogram of Calibration Mixtu
36、re Using Conditions in Table 2D7266 134TABLE 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(11) cyclohexeneA(12
37、) 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-dimethylcyclopentane(22) 2,2-dimethylcy
38、clopentane(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) isopropylcylohexaneATABLE 1 Impurities Known or Sugges
39、ted 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) 2,2-dimethylbutane(13) 2,3-dimethylbutaneC7(14) 3,3-dimethylpentane(15) 2,2-dim
40、ethylpentane(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(23) 2,4-dimethylcyclopentane(24) cis-1,3-dimethylcyclopentane(25) ethylcyclope
41、ntane(26) methylcyclohexane(27) 3-ethylpentane(28) 3-methylhexaneD7266 13511.3 Determine the response factor for each impurity in the calibration mixture as follows:Rfi 5CiAi(1)where:where:Rfi = response factor for impurity i,Ci = concentration of impurity i in the calibration mixture, andAi = peak
42、area of impurity i.11.4 Initially analyze the calibration solution a minimum of three times and calculate an average Rfi. Subsequent calibrationsmay be a single analysis as long as the response factors for all components of interest are within 65 % of the initial validationresponse factors.A“rolling
43、” average as defined by most modern chromatographic software may also be used. The response factorfor n-hexane is used for unknowns.12. Procedure12.1 Inject into the gas chromatograph an appropriate amount of sample as previously determined in accordance with 6.1 andstart the analysis.12.2 Obtain a
44、chromatogram and peak integration report.13. Calculations13.1 Calculate the concentration of each impurity as follows:Ci 5Ai! Rfi! (2)where: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
45、of all impurities in wt % as follows:Ct 5 (Ci10000 (3)where:where:Ct = total concentration of all impurities in wt %.13.3 Calculate the purity of cyclohexane as follows:Cyclohexane,weight percent5100.002Ct (4)14. Report14.1 Report the individual impurities to the nearest mg/kg.14.2 Report the purity
46、 of cyclohexane to the nearest 0.01 wt %.15. Precision and Bias515.1 An ILS was conducted which included two laboratories analyzing five samples three times. One lab analyzed the sampleson two different instruments. Practice E691 was followed for the design and analysis of the data; this ILS did not
47、 meet PracticeE691 minimum requirements of six labs, four materials, and two replicates. The details are given in ASTM Research Report No.RR:D16-1045.5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D16-1045. Contact ASTM Custo
48、merService at serviceastm.org.(29) 2-methylhexane(30) n-heptane(31) tolueneC8(32) iso-octane(33) p-xyleneC9(34) isopropylcylohexaneA These components were used to prepare the standard used in the repeatabilityprogram.D7266 13615.2 Repeatability (r)Results should not be suspect unless they differ by
49、more than shown in Tables 3-7. Results differing byless than “r” have a 95 % probability of being correct.15.3 RepeatabilityReproducibility (R)Results within the same laboratory by the same operator with the same equipmentover the shortest practical period of time submitted by two labs should not be considered suspect unless they differ by more thanthe amounts shown in Table 3Tables 3-7.Asingle sample was analyzed 20Results differing by less than “R times over the shortestpractical time.” have a 95 % probability of being correct.TABLE 4 Benze
