1、Designation: D7360 16Standard Test Method forAnalysis of Benzene by Gas Chromatography with ExternalCalibration1This standard is issued under the fixed designation D7360; 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.1. Scope*1.1 This test method covers the determination of normallyoccurring trace impurities in, and the purity of, finishedbenzen
3、e by gas chromatography with external calibration. Asimilar test method, using the internal standard technique ofcalibration is Test Method D4492.1.2 This test method is applicable for nonaromatic hydro-carbon impurities at levels from 5 to 2000 mg/kg and forbenzene purities of 99.80 weight % or hig
4、her.1.3 This test method is applicable for aromatic impuritiesfrom 5 to 2000 mg/kg in benzene.1.4 This test method has been found applicable to hetero-atomic species such as 1,4-dioxane, from 10 to 2000 mg/kg inbenzene.1.5 The limit of detection for aromatic impurities is 0.9mg/kg, 2.7 mg/kg for 1,4
5、-dioxane and 1.1 mg/kg for methylcyclohexane.1.6 In determining the conformance of the test results usingthis method to applicable specifications, results shall berounded off in accordance with the rounding-off method ofPractice E29.1.7 The values stated in SI units are to be regarded asstandard. No
6、 other units of measurement are included in thisstandard.1.8 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 and health practices and determine the applica-bili
7、ty of regulatory limitations prior to use. For specific hazardstatements, see Section 9.2. Referenced Documents2.1 ASTM Standards:2D3437 Practice for Sampling and Handling Liquid CyclicProductsD3798 Test Method for Analysis of p-Xylene by Gas Chro-matography (Withdrawn 2009)3D4307 Practice for Prepa
8、ration of Liquid Blends for Use asAnalytical StandardsD4492 Test Method for Analysis of Benzene by Gas Chro-matographyD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Pra
9、ctice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-shipsE1510 Practice for Instal
10、ling Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:4OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.12003. Terminology3.1 See Terminology D4790 for definition of terms used inthis test method.1This test method is under the jurisdiction of ASTM Committee D16
11、 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.01 on Benzene, Toluene, Xylenes, Cyclohexane and TheirDerivatives.Current edition approved Nov. 1, 2016. Published January 2017. Originallyapproved in 2011. Last previous edition approved in 2011 as D7
12、360 11. DOI:10.1520/D7360-16.2For 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.3The last approved version of th
13、is historical standard is referenced onwww.astm.org.4Available 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 Inter
14、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,
15、Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.14. Summary of Test Method4.1 A repeatable volume of the specimen to be analyzed isprecisely injected into a gas chromatograph equipped with aflame ionization detector (FID) and a capillary
16、column.4.2 The peak area of each impurity is measured. Theconcentration of each impurity is determined using responsefactor or the linear calibration curve of peak area versusconcentration. Purity is calculated by subtracting the sum ofthe impurities found from 100.00 weight %. The concentrationof i
17、mpurities are reported in mg/kg. Purity of benzene isreported in weight percent.5. Significance and Use5.1 This test method is suitable for determining the concen-trations of known impurities in finished benzene and for use asan integral quality control tool where benzene is either pro-duced or used
18、 in a manufacturing procedure. It is generallyapplied to impurities such as nonaromatics containing ninecarbons or less, toluene, C8 aromatics, and 1,4-dioxane.5.2 Absolute purity cannot be determined if undetectedimpurities are present.6. Interferences6.1 Benzene is typically resolved from componen
19、ts withboiling points 138C that normally are found in purifiedbenzene. Components normally found in purified benzeneinclude nonaromatic hydrocarbons, toluene, C8 aromatics, and1,4-dioxane. An adequate separation of known impurities frombenzene should be evaluated for the column selected.7. Apparatus
20、7.1 Gas Chromatograph, any chromatograph having a flameionization detector that can be operated at the conditions givenin Table 1.7.2 Electronic Integrator chromatography data system.7.3 Column, fused silica capillary column with cross-linkedpolyethylene glycol stationary phase is recommended. Alter
21、-nate stationary phases may be used if they produce at least thesame aromatic separation as achieved in the chromatogram inFig. 1 and elute C9nonaromatic impurities before benzene.7.4 Automatic InjectorThe sample must be precisely andrepeatably injected into the gas chromatograph. An automaticsample
22、 injection device is highly recommended.8. Reagents and Materials8.1 Carrier Gas, 99.999 % helium or hydrogen. Concentra-tion of oxygen in the carrier should be 1 ppm, 0.5 ppm ispreferred.8.2 Detector Gases, 99.999 %Nitrogen is recommendedfor make up 99.999 %. Hydrogen with THC 0.5 mg/kg. Airwith CO
23、2, CO and THC 1 mg/kg and oxygen between 20 and22 %, is recommended.8.3 High Purity Benzene, 99.999 weight % minimum,prepared by multiple step recrystallization of commerciallyavailable 99 + weight % benzene. See Annex A1. The benzenemust be recrystalized a minimum of three times and thenanalyzed us
24、ing this test method. Continue recrystalizing thebenzene until no impurity greater than three times the noiselevel is detected.8.4 Pure compounds for calibration should include toluene,o-, m-, and p-xylene, ethylbenzene, methylcyclohexane, and1,4-dioxane of a purity not less than 99 %. If the purity
25、 of thecalibration compounds is less than 99 %, the concentration andidentification of impurities must be known so that the compo-sition of the final weighed blends can be adjusted for thepresence of the impurities.FIG. 1 Typical ChromatogramTABLE 1 Typical Instrumental ParametersDetector flame ioni
26、zationColumn: fused silicaLength 50 mInside diameter 0.32 mmStationary phase crosslinked polyethyleneglycolFilm thickness 0.25 mTemperatures:Injector 200CDetector 250CColumn 70C isothermalCarrier gas: heliumLinear velocity 22 cm/sSplit ratio: 100:1Sample size 2.0 LRecorder electronic integrationrequ
27、iredD7360 1629. Hazards9.1 Consult current OSHA regulations and suppliers SafetyData Sheets and local regulations for all materials used in thistest method.9.2 Benzene is considered a hazardous material. The sam-pling and testing of benzene should follow safety rules in orderto adhere to all safety
28、precautions as outlined in current OSHAregulations.10. Sampling10.1 Sample the material in accordance with PracticeD3437.11. Preparation of Apparatus11.1 Follow manufacturers instructions for installing thecolumn into the chromatograph and adjusting the instrument tothe conditions described in Table
29、 1. Other conditions may beused as long as the same level of precision is achieved. Allowsufficient time for the equipment to reach equilibrium. SeePractices E260, E1510 and E355 for additional information ongas chromatography practices and terminology.12. Calibration12.1 Prepare synthetic mixtures
30、of high purity benzene andrepresentative impurities by direct weighing. Weigh eachimpurity to the nearest 0.1 mg. Table 2 contains a typicalcalibration blend. Methylcyclohexane is used for the non-aromatic portion.12.1.1 It has been determined that the detector is linear to2000 mg/kg.12.2 Using the
31、exact weight for each impurity, calculate themg/kg concentration of the calibration blends, in accordancewith Practice D4307, being sure to correct for impurities in thebenzene as described therein. This standard may be purchasedif desired.12.3 Inject 2 L, or other appropriate volume, that will give
32、precision stated in precision statement, into the chromatographand integrate the area under each peak, excluding benzene.12.4 Determine the response factor for each impurity in thecalibration mixture as follows:Rfi5 Ci/Ai(1)where:Rfi= response factor for impurity i,Ci= concentration of the impurity
33、i in the calibrationmixture, (mg/kg), andAi= peak area of impurity i.12.5 Initially analyze the calibration solution a minimum ofthree times and calculate an average Rfi.13. Procedure13.1 Inject 2 L, or other appropriate volume of sample intothe chromatograph. The size and conditions of the samplein
34、jection shall be the same as the injected standard used forcalibration.13.2 Integrate the area under all peaks except for benzene.Sum the nonaromatic fraction eluting before benzene forreporting as a single component. See Fig. 1 for a typicalchromatogram.14. Calculation14.1 Calculate the concentrati
35、on of each impurity as fol-lows:Ci5 Ai3 Rfi(2)where:Ci= concentration of the impurity, mg/kg,Ai= average peak i area, andRfi= response factor for the impurity i.14.2 Calculate the benzene purity as follows:Benzene weight % 5 100 2 Ct (3)where:Ct = total concentration of all impurities, weight %, cal
36、cu-lated this way:Ct 5(iCimg/kg!/10000 mg/kg/weight %! (4)15. Quality Assurance/Quality Control (QA/QC)15.1 Laboratories shall have a quality control system inplace.15.2 Confirm the performance of the test instrument or testmethod by analyzing a quality control sample following theguidelines of stan
37、dard statistical quality control practices.15.3 A quality control sample is a stable material isolatedfrom the production process and representative of the samplebeing analyzed.15.4 When QA/QC protocols are already established in thetesting facility, these protocols are acceptable when theyconfirm t
38、he validity of test results.15.5 When there are no QA/QC protocols established in thetesting facility, use the guidelines described in Guide D6809 orsimilar statistical quality control practices.16. Report16.1 Report the following information:16.1.1 Benzene and the total impurities to the nearest0.0
39、1 % and16.1.2 Individual impurities to the nearest 1 mg/kg.TABLE 2 Typical Calibration Blend, mg/kgBenzene 99.8 (wt %)Toluene 250Methylcyclohexane 250Ethylbenzene 250p-Xylene 250m-Xylene 250o-Xylene 2501,4-Dioxane 250D7360 16317. Precision and Bias517.1 A single sample with components near the limit
40、 ofdetection was analyzed 20 times by one person using oneinstrument over the shortest practical time. A second samplenear the upper limit of the method was also analyzed 20 timesby one person using one instrument over the shortest practicaltime. Details are given in Research Report No. RR:D16-1042.
41、17.2 Repeatability:17.2.1 Results should not be suspect unless they differ bymore than shown in Table 3 and Table 4. Results that differ byless than “r” have a 95 % probability of being correct.17.3 Reproducibility has not been determined and will bedetermined within five years.17.4 BiasSince there
42、is no accepted reference materialsuitable for determining the bias in this test method, bias hasnot been determined.18. Keywords18.1 benzene; gas chromatography; purityANNEX(Mandatory Information)A1. RECRYSTALIZATION OF BENZENEA1.1 A schematic of the process is shown in Fig. A1.1: thebenzene is froz
43、en slowly overnight at 4C, just below itsmelting point of 5.5C. The result is a bulk of frozen benzenewith a liquid cover comprised of a blend of benzene andconcentrated contaminants. This liquid is discarded and thebenzene is allowed to melt for analysis. This test should give acleaner chromatogram
44、 for the benzene since the contaminantsstayed in liquid phase. This process is repeated until noimpurity with a peak area three times the noise level isdetected. A minimum of three recrystalizations is required andmay require up to seven cycles.5Supporting data have been filed at ASTM International
45、Headquarters and maybe obtained by requesting Research Report RR:D16-1042. ContactASTM CustomerService at serviceastm.org.TABLE 3 Concentration (mg/kg) 99.9979 % BenzeneAnalyte AverageRepeatabilityLimitXrMethylcyclohexane 3 1Toluene 3 11,4-Dioxane 4 3Ethylbenzene 3 1p-Xlyene 3 1m-Xylene 3 1o-Xylene
46、3 1Benzene (wt % ) 99.9979 0.0004TABLE 4 Concentration (mg/kg) 99.77 % BenzeneAnalyte AverageRepeatabilityLimitXrMethylcyclohexane 330 40Toluene 270 401,4-Dioxane 400 80Ethylbenzene 320 40p-Xlyene 320 65m-Xylene 340 64o-Xylene 320 50Benzene (wt % ) 99.77 0.02D7360 164SUMMARY OF CHANGESCommittee D16
47、has identified the location of selected changes to this standard since the last issue (D736011)that may impact the use of this standard. (Approved November 1, 2016.)(1) Added Summary of Changes section.(2) Reference to Material Safety Data Sheet corrected to SafetyData Sheet.ASTM International takes
48、 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, and the riskof infringement of such rights, are entirely their own resp
49、onsibility.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 revision 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 shouldmake your views known to the
