1、Designation: D 4492 07Standard Test Method forAnalysis of Benzene by Gas Chromatography1This standard is issued under the fixed designation D 4492; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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, finishedbenzene by gas chromatograph
3、y.1.2 This test method is applicable for benzene purities of99.80 weight % or higher.1.3 The lower limit of detection for total non-aromaticimpurities is 0.005 weight %. The lower limit of detection forindividual aromatic hydrocarbon impurities in 0.001 weight %.The lower limit of detection for 1,4-
4、dioxane is 0.0005 weight%.1.4 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 E29.1.5 The values stated in SI units are to be regarded asstandard. No other units of mea
5、surement 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 theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory li
6、mitations prior to use. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 852 Test Method for Solidification Point of BenzeneD 3437 Practice for Sampling and Handling Liquid CyclicProductsD 6809 Guide for Quality Control and Quality AssuranceProcedures for Aro
7、matic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 260 Practice for Packed Column Gas ChromatographyE 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 691 Practice for Conducting an Interlaboratory
8、 Study toDetermine the Precision of a Test MethodE 1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120033. Summary of Test Method3.1 A known amount of an internal standard is added t
9、o thespecimen. A small volume of this mixture is injected into a gaschromatograph equipped with a flame ionization detector (FID)and a capillary column.3.2 The peak area of each impurity and the internal standardis measured by an electronic integrator. The concentration ofeach impurity is calculated
10、 from the ratio of the peak area ofthe internal standard versus the peak area of the impurity.Purity is calculated by subtracting the sum of the impuritiesfound from 100.00 weight %. Results are reported in weightpercent.4. Significance and Use4.1 This test method is suitable for determining the con
11、cen-trations 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
12、.4.2 Absolute purity cannot be determined if unknown im-purities are present. Test Method D 852 is generally used as acriteria for determining the absolute purity.5. Interferences5.1 Benzene is typically resolved from naturally occurringcomponents with boiling points 138C. Naturally occurringcompone
13、nts include nonaromatic hydrocarbons, toluene, C81This 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 appro
14、ved June 1, 2007. Published June 2007. Originallyapproved in 1985. Last previous edition approved in 2003 as D 4492 - 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refe
15、r to the standards Document Summary page 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.1*A Summary of Changes section appears at the end of this standard.Copyright
16、ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.aromatics, and 1,4-dioxane. An adequate separation of knownimpurities from benzene should be evaluated for the columnselected.5.2 The internal standard chosen must be sufficiently re-solved from a
17、ny impurity and the benzene peak.6. Apparatus6.1 Gas ChromatographAny chromatograph having aflame ionization detector that can be operated at the conditionsgiven in Table 1. The system should have sufficient sensitivityto obtain a minimum peak height response for a 0.0005 weight% impurity three time
18、s the height of the signal backgroundnoise.6.2 Electronic Integrator, computer-based capable of han-dling internal standard calculations and peak grouping isrecommended.6.3 Column, fused silica capillary column with cross-linkedpolyethylene glycol stationary phase is recommended. Alter-nate stationa
19、ry phases may be used if they produce at least thesame aromatic separation and elute C9nonaromatic impuritiesbefore benzene.6.4 Microsyringes, 10 and 100 l capacity.7. Reagents and Materials7.1 Carrier GasChromatographic grade helium is recom-mended.7.2 High Purity Benzene, 99.99 weight % minimum, p
20、re-pared by multiple step recrystallization of commercially avail-able 99 + weight % benzene.7.3 Internal Standard, n-Nonane (nC9) with a purity of 99weight % minimum is recommended. Other compounds maybe acceptable provided they can be obtained in high purity andmeet the requirements of 5.2.7.4 Pur
21、e compounds for calibration should include toluene,benzene, ethylbenzene, cyclohexane, and 1,4-dioxane of apurity not less than 99 %. If the purity of the calibrationcompounds is less than 99 %, the concentration and identifi-cation of impurities must be known so that the composition ofthe final wei
22、ghed blends can be adjusted for the presence of theimpurities.8. Hazards8.1 Consult current OSHA regulations and suppliers Mate-rial Safety Data Sheets and local regulations for all materialsused in this test method.8.2 Benzene is considered a hazardous material. The sam-pling and testing of benzene
23、 should follow safety rules in orderto adhere to all safety precautions as outlined in current OSHAregulations.9. Sampling9.1 Sample the material in accordance with PracticeD 3437.10. Preparation of Apparatus10.1 Follow manufacturers instructions for mounting thecolumn into the chromatograph and adj
24、usting the instrument tothe conditions described in Table 1. Allow sufficient time forthe equipment to reach equilibrium. See Practices E 260,E 1510 and E 355 for additional information on gas chroma-tography practices and terminology.11. Calibration11.1 Prepare a synthetic mixture of high purity be
25、nzene andrepresentative impurities by direct weighing. Weigh eachimpurity to the nearest 0.1 mg. Table 2 contains a typicalcalibration blend. Cyclohexane is used for the nonaromaticportion and ethylbenzene for the C8aromatic portion. Thisstandard may be purchased if desired.11.2 Using the exact weig
26、ht for each impurity, calculate theweight % concentration of the calibration blend.11.3 Partly fill a 50-mL volumetric flask with the calibrationblend, add 50 L of nC9, dilute to the mark with the calibrationblend, and mix well. Using a density of 0.874 g/mL for thecalibration blend and a density of
27、 0.718 g/mL for the nC9, theresulting nC9concentration will be 0.0825 weight %. Alternatevolumes of solutions may be prepared so long as the prepara-tion meets the concentration specified.11.4 Inject 0.5 L, or other appropriate volume, of the blendwith internal standard into the chromatograph and in
28、tegrate thearea under each peak, excluding benzene.11.5 Calculate the relative response factors (RRF) as fol-lows:RRFi5 As!Ci!/Cs!Ai! (1)where:RRFi= RRF for impurity i,As= peak area of internal standard,Ai= peak area of impurity i,Ci= weight % for impurity i, from 11.2,Cs= concentration of internal
29、standard, weight % from11.3.TABLE 1 Typical Instrumental ParametersDetector flame ionizationColumn: fused silicaLength 50 mInside diameter 0.32 mmStationary phase crosslinked polyethylene glycolFilm thickness 0.25 mTemperatures:Injector 200CDetector 250CColumn 70C isothermalCarrier gas: heliumLinear
30、 velocity 22 cm/sSplit ratio: 200:1Makeup gas helium or nitrogenSample size 0.5 LRecorder electronic integration requiredTABLE 2 Typical Calibration Blend, gBenzene 99.0000Toluene 0.0500Cyclohexane 0.0500Ethylbenzene 0.05001,4 Dioxane 0.0200D449207212. Procedure12.1 Into a 50-mL volumetric flask, ad
31、d 50 L of nC9internal standard and dilute to the mark with specimen. Mixwell. Alternate volumes of solutions may be prepared so longas the preparation meets the concentration specified.12.2 Inject 0.5 L, or other appropriate volume of mixtureinto the chromatograph.12.3 Integrate the area under all p
32、eaks except for benzene.Sum the nonaromatic fraction up to nC9for reporting as asingle component. See Fig. 1 for a typical chromatogram.13. Calculation13.1 Calculate the amounts of each individual impurity asrequired. Sum the areas of all the nonaromatic peaks.13.2 Calculate the weight % concentrati
33、on of each impurityas follows:Ci5 Ai!RRFi!Cs!/As! (2)13.3 Calculate the benzene purity as follows:Benzene, weight % 5 100.00 2 Ct(3)where:Ct= total concentration of all impurities, weight %.14. Report14.1 Report the following information:14.1.1 Benzene and the total impurities to the nearest0.01 % a
34、nd14.1.2 Individual impurities to the nearest 0.001 %. Ifneeded, 1,4-dioxane may be reported down to 0.0005 weight%.15. Precision and Bias415.1 PrecisionThe following criteria should be used tojudge the acceptability of results obtained by this test method(95 % confidence level). The precision crite
35、ria was derivedfrom an interlaboratory study by six different laboratories.Each sample was run twice in two days by two differentoperators. The precision criteria for 1,4-dioxane was derivedfrom an interlaboratory study by nine different laboratories.Each sample was run twice in two days by two diff
36、erentoperators. Results of the interlaboratory study data wereanalyzed in accordance with Practice E 691.15.2 Intermediate PrecisionDuplicated results by thesame operator should not be considered suspect unless theydiffer by more than 6 the amount shown in Table 3.15.3 ReproducibilityThe results bet
37、ween two laboratoriesshould not be considered suspect unless they differ by morethan 6 the amount shown in Table 3.15.4 BiasSince there was no accepted reference materialavailable at the time of interlaboratory testing, no statement onbias can be made at this time.4Supporting data are available from
38、 ASTM International Headquarters. RequestRR: D16-1005.FIG. 1 Typical ChromatogramD449207316. Quality Guidelines16.1 Refer to Guide D 6809 for suggested QA/QC activitiesthat can be used as a part of this test method. It is recom-mended that the operator of this test method select and performrelevant
39、QA/QC activities like the ones on Guide D 6809 tohelp ensure the quality of data generated by this test method.17. Keywords17.1 benzene; gas chromatography; puritySUMMARY OF CHANGESCommittee D16 has identified the location of selected changes to this standard since the last issue(D 4492 - 03) that m
40、ay impact the use of this standard. (Approved June 1, 2007.)(1) Modified 1.3, 6.1, and 14.1.2 to allow reporting of 1,4-dioxene down to 0.0005 % and adjusted lower limits ofdetection based upon the S0calculation.(2) Modified 1.4, Footnote 2, and 15.1 to conform to currenteditorial guidelines.(3) Add
41、ed Quality Guidelines, Section 16, per editorial guide-lines.(4) Modified 11.3 for ease of use.(5) Added makeup gas to Table 1.ASTM 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
42、expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not re
43、vised, 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
44、may attend. If you feel that your comments have not received a fair hearing 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 S
45、tates. Individual reprints (single or multiple copies) of this standard 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).TABLE 3 Benzene Purity Intermediate Precision andRepro
46、ducibilityComponentConcentration (mg/kg)AverageConcentrationIntermediatePrecisionReproducibilityNonaromatics 22 19 20737 70 184Toluene 14 2 6116 4 54Ethylbenzene 14 3 7121 7 14p-Xylene 13 3 5110 5 16m-Xylene 44 5 9162 9 17o-Xylene 14 5 1889 7 81,4 Dioxane 10 2.3 4.85 1.9 2.5100 3.0 9.0Benzene (wt %) 99.87 0.01 0.02799.99 0.002 0.004D4492074
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