1、Designation: D 7360 11Standard Test Method forAnalysis of Benzene by Gas Chromatography with ExternalCalibration1This standard is issued under the fixed designation D 7360; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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. Scope1.1 This test method covers the determination of normallyoccurring trace impurities in, and the purity of, finishedbenze
3、ne 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 hi
4、gher.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,
5、4-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. N
6、o 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-bil
7、ity 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 GasChromatography3D4307 Practice for Preparation of Liquid B
8、lends for Use asAnalytical StandardsD4492 Test Method for Analysis of Benzene by Gas Chro-matographyD4790 Terminology ofAromatic Hydrocarbons and RelatedChemicalsD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Sig
9、nificant 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 Rela-tionshipsE1510 Practice for Installing Fused Silica O
10、pen 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.4. Summary of Test Method4.1 A repeatable volume of the specimen to be analyzed ispr
11、ecisely injected into a gas chromatograph equipped with aflame ionization detector (FID) and a capillary 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. Purit
12、y is calculated by subtracting the sum of1This test method 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 June
13、 1, 2011. Published July 2011. DOI: 10.1520/D736011.2For 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.3Withdraw
14、n. The last approved version of this historical standard is referencedon www.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.1Copyright ASTM International, 100 Barr Harbor Driv
15、e, PO Box C700, West Conshohocken, PA 19428-2959, United States.the impurities found from 100.00 weight %. The concentrationof impurities 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
16、of known impurities in finished benzene and for use asan integral quality control tool where benzene is either pro-duced or used 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
17、 purity cannot be determined if undetectedimpurities are present.6. Interferences6.1 Benzene is typically resolved from components withboiling points 138C that normally are found in purifiedbenzene. Components normally found in purified benzeneinclude nonaromatic hydrocarbons, toluene, C8 aromatics,
18、 and1,4-dioxane. An adequate separation of known impurities frombenzene should be evaluated for the column selected.7. Apparatus7.1 Gas Chromatograph, any chromatograph having a flameionization detector that can be operated at the conditions givenin Table 1.7.2 Electronic Integrator chromatography d
19、ata system.7.3 Column, fused silica capillary column with cross-linkedpolyethylene glycol stationary phase is recommended. Alter-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
20、benzene.7.4 Automatic InjectorThe sample must be precisely andrepeatably injected into the gas chromatograph. An automaticsample 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
21、ppm ispreferred.8.2 Detector Gases, 99.999 %Nitrogen is recommendedfor make up 99.999 %. Hydrogen with THC 0.5 mg/kg. Airwith CO2, 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 commerci
22、allyavailable 99 + weight % benzene. See Annex A1. The benzenemust be recrystalized a minimum of three times and thenanalyzed using this test method. Continue recrystalizing thebenzene until no impurity greater than three times the noiselevel is detected.8.4 Pure compounds for calibration should inc
23、lude toluene,o-, m-, and p-xylene, ethylbenzene, methylcyclohexane, and1,4-dioxane of a purity not less than 99 %. If the purity 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
24、adjusted for thepresence of the impurities.9. Hazards9.1 Consult current OSHA regulations and suppliers Mate-rial Safety Data Sheets and local regulations for all materialsused in this test method.9.2 Benzene is considered a hazardous material. The sam-pling and testing of benzene should follow safe
25、ty rules in orderto adhere to all safety precautions as outlined in current OSHAregulations.FIG. 1 Typical ChromatogramTABLE 1 Typical Instrumental ParametersDetector flame ionizationColumn: fused silicaLength 50 mInside diameter 0.32 mmStationary phase crosslinked polyethylene glycolFilm thickness
26、0.25 mTemperatures:Injector 200CDetector 250CColumn 70C isothermalCarrier gas: heliumLinear velocity 22 cm/sSplit ratio: 100:1Sample size 2.0 LRecorder electronic integration requiredD736011210. Sampling10.1 Sample the material in accordance with PracticeD3437.11. Preparation of Apparatus11.1 Follow
27、 manufacturers instructions for installing thecolumn into the chromatograph and adjusting the instrument tothe conditions described in Table 1. Other conditions may beused as long as the same level of precision is achieved. Allowsufficient time for the equipment to reach equilibrium. SeePractices E2
28、60, E1510 and E355 for additional information ongas chromatography practices and terminology.12. Calibration12.1 Prepare synthetic mixtures of high purity benzene andrepresentative impurities by direct weighing. Weigh eachimpurity to the nearest 0.1 mg. Table 2 contains a typicalcalibration blend. M
29、ethylcyclohexane 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 exact weight for each impurity, calculate themg/kg concentration of the calibration blends, in accordancewith Practice D4307, being sure to correct for impuriti
30、es in thebenzene as described therein. This standard may be purchasedif desired.12.3 Inject 2 L, or other appropriate volume, that will giveprecision stated in precision statement, into the chromatographand integrate the area under each peak, excluding benzene.12.4 Determine the response factor for
31、each impurity in thecalibration mixture as follows:Rfi5 Ci/Ai(1)where:Rfi= response factor for impurity i,Ci= concentration of the impurity 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 av
32、erage Rfi.13. Procedure13.1 Inject 2 L, or other appropriate volume of sample intothe chromatograph. The size and conditions of the sampleinjection 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 e
33、luting before benzene forreporting as a single component. See Fig. 1 for a typicalchromatogram.14. Calculation14.1 Calculate the concentration 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
34、.14.2 Calculate the benzene purity as follows:Benzene weight % 5 100 Ct (3)where:Ct = total concentration of all impurities, weight %, calcu-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 in
35、place.15.2 Confirm the performance of the test instrument or testmethod by analyzing a quality control sample following theguidelines of standard statistical quality control practices.15.3 A quality control sample is a stable material isolatedfrom the production process and representative of the sam
36、plebeing analyzed.15.4 When QA/QC protocols are already established in thetesting facility, these protocols are acceptable when theyconfirm the 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 st
37、atistical quality control practices.16. Report16.1 Report the following information:16.1.1 Benzene and the total impurities to the nearest0.01 % and16.1.2 Individual impurities to the nearest 1 mg/kg.17. Precision and Bias517.1 A single sample with components near the limit ofdetection was analyzed
38、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. D161042.17.2 Repeatability:17.2.1 Resu
39、lts 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 is no accepted reference mater
40、ialsuitable for determining the bias in this test method, bias hasnot been determined.5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1042.TABLE 2 Typical Calibration Blend, mg/kgBenzene 99.8 (wt %)Toluene 250Methylcyclohexa
41、ne 250Ethylbenzene 250p-Xylene 250m-Xylene 250o-Xylene 2501,4-Dioxane 250D736011318. 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 frozen slowly overnight at 4C, just bel
42、ow 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 for the benzene since the contamin
43、antsstayed 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.TABLE 3 Concentration (mg/kg) 99.9979 % BenzeneAnalyte AverageRepeatabilityLimitX rMethylc
44、yclohexane 3 1Toluene 3 11,4-Dioxane 4 3Ethylbenzene 3 1p-Xlyene 3 1m-Xylene 3 1o-Xylene 3 1Benzene (wt %) 99.9979 0.0004TABLE 4 Concentration (mg/kg) 99.77 % BenzeneAnalyte AverageRepeatabilityLimitX rMethylcyclohexane 330 40Toluene 270 401,4-Dioxane 400 80Ethylbenzene 320 40p-Xlyene 320 65m-Xylene
45、 340 64o-Xylene 320 50Benzene (wt %) 99.77 0.02D7360114ASTM International takes 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
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48、ing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard
49、may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. A1.1 SchematicD7360115
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