1、Designation: D7504 091Standard Test Method forTrace Impurities in Monocyclic Aromatic Hydrocarbons byGas Chromatography and Effective Carbon Number1This standard is issued under the fixed designation D7504; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year 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.1NOTETable 1 was corrected editorially in March 2010.1. Scope1.1 This test method covers the d
3、etermination of the totalnonaromatic hydrocarbons and trace monocyclic aromatichydrocarbons in toluene, mixed xylenes, and p-xylene by gaschromatography. The purity of toluene, mixed xylenes, orp-xylene can also be calculated. Similar test methods, using theinternal standard calibration technique an
4、d the external stan-dard calibration technique, are Test Method D2360 and D5917respectively.1.2 Total aliphatic hydrocarbons containing 1 through 10carbon atoms (methane through decanes) can be detected bythis test method at concentrations ranging from 0.0001 to2.5000 weight %. The limit of detectio
5、n is 0.00003 weight %and the limit of quantitation is 0.0001 weight %.1.2.1 A small amount of benzene in mixed xylenes orp-xylene may not be distinguished from the non-aromatics andthe concentrations are determined as a composite (see 6.1).1.3 Monocyclic aromatic hydrocarbon impurities containing6 t
6、hrough 10 carbon atoms (benzene through C10aromatics)can be detected by this test method at individual concentrationsranging from 0.0001 to 1.0000 weight %.1.4 The following applies to all specified limits in this testmethod: for purposes of determining conformance with thistest method, an observed
7、value or a calculated value shall berounded off “to the nearest unit” in the last right-hand digitused in expressing the specification limit, in accordance withthe rounding-off method of Practice E29.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are i
8、ncluded 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 limitations prio
9、r to use.2. Referenced Documents2.1 ASTM Standards:2D841 Specification for Nitration Grade TolueneD2360 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas ChromatographyD3437 Practice for Sampling and Handling Liquid CyclicProductsD4534 Test Method for Benzene Content of Cycl
10、ic Prod-ucts by Gas Chromatography3D4790 Terminology ofAromatic Hydrocarbons and RelatedChemicalsD5136 Specification for High Purity p-XyleneD5211 Specification for Xylenes for p-Xylene FeedstockD5917 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas Chromatography andExtern
11、al CalibrationD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE26
12、0 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Rela-tionshipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.
13、2 Other Document:1This 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 Jan. 15, 2009. Published Feb
14、ruary 2009. DOI:10.1520/D7504-09.2For 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.3Withdrawn. The last approve
15、d version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120043. Terminology3.1 See Terminology D4790 for definitions of
16、terms used inthis test method.4. Summary of Test Method4.1 The specimen to be analyzed is injected into a gaschromatograph equipped with a flame ionization detector (FID)and a capillary column. The peak area of each component ismeasured and adjusted using effective carbon number (ECN)5response facto
17、rs. The concentration of each component iscalculated based on its relative percentages of total adjustedpeak area and normalized to 100.0000 %.5. Significance and Use5.1 Determining the type and amount of hydrocarbon im-purities remaining from the manufacture of toluene, mixedxylenes, and p-xylene u
18、sed as chemical intermediates andsolvents is often required. This test method is suitable forsetting specifications and for use as an internal quality controltool where these products are produced or are used. Typicalimpurities are: alkanes containing 1 to 10 carbons atoms,benzene, toluene, ethylben
19、zene (EB), xylenes, and aromatichydrocarbons containing nine carbon atoms.5.2 This method may not detect all components and theremay be unknown components that would be assigned inappro-priate response factors and thus, the results may not beabsolute.6. Interferences6.1 In some cases for mixed xylen
20、es and p-xylene, it may bedifficult to resolve benzene from the nonaromatic hydrocar-bons. Therefore the concentrations are determined as a com-posite. In the event that the benzene concentration must bedetermined, an alternate method such as Test Method D4534must be selected to ensure an accurate a
21、ssessment of thebenzene concentration.6.2 Complete separation of ethylbenzene and m-xylene forp-xylene is difficult and can be considered adequate if thedistance from baseline to valley between peaks is not greaterthan 50 % of the peak height of the impurity.7. Apparatus7.1 Chromatographic data syst
22、em is required.7.2 ColumnsThe choice of column is based on resolutionrequirements. Any column may be used that is capable ofresolving all significant impurities from the major component.The column and conditions described in Table 1 have beenused successfully and shall be used as a referee in cases
23、ofdispute.7.3 Gas ChromatographAny instrument having a flameionization detector and a splitter injector suitable for use witha fused silica capillary column may be used, provided thesystem has sufficient sensitivity, linearity, and range to deter-mine 0.0001 wt %, while not exceeding the full scale
24、of eitherthe detector or the electronic integration for the major compo-nent. It shall have a split injection system that will notdiscriminate over the boiling range of the samples analyzed.The system should be capable of operating at conditions givenin Table 1.7.4 InjectorThe specimen must be preci
25、sely and repeat-ably injected into the gas chromatograph.An automatic sampleinjection devise is highly recommended.7.5 Syringe, chromatographic, capable of delivering appro-priate L volumes.8. Reagents and Materials8.1 Purity of ReagentReagent grade chemicals shall beused in all tests. Unless otherw
26、ise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society,6where such specifications are available. Reagents with anestablish purity greater than ACS reagent grade may be used.8.2 Carrier Gas, makeup gas
27、 and detector gases 99.999 %pure. Oxygen in carrier gas less than 1 ppm, less than 0.5 ppmis preferred. Purify carrier, makeup and detector gases toremove oxygen, water, and hydrocarbons.8.3 Air for the FID should contain less than 0.1 ppm totalhydrocarbon.8.4 Calibration check standard. This standa
28、rd may bepurchased if desired.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.5Scanlon. J. T. and Willis, D. E., “Calculation of Flame Ionization DetectorRelative Response Factors Using
29、 the Effective Carbon Number Concept,” Journalof Chromatographic Science, Vol. 35, August 1985, pp. 333339.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, se
30、e Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 1 Recommended Method ParametersInlet SplitTemperature, C 270Column:Tubing fused silicaLength, m 60Intern
31、al diameter, mm 0.32Stationary phase crosslinked polyethyleneglycolFilm thickness, m 0.25Column temperature programInitial temperature, C 60Initial time, min 10Programming rate, C/min 5Final, C 150Time 2, min 10Carrier gas helium or hydrogenLinear velocity, cm/s at 145C 20 helium or 45 hydrogenSplit
32、 ratio 100:1Sample size, L 0.6Detector: flame ionizationTemperature, C 300Analysis time, min 38D7504 09129. Hazards9.1 Consult current OSHA regulations, suppliers MaterialSafety Data Sheets, and local regulations for all materials usedin this test method.10. Sampling10.1 Sample the material in accor
33、dance with PracticeD3437.11. Preparation of Apparatus11.1 Follow manufacturers instructions for mounting andconditioning the column into the chromatograph and adjustingthe instrument to the conditions described in Table 1, allowingsufficient time for the equipment to reach equilibrium. SeePractices
34、E260, E355, and E1510 for additional information ongas chromatography practices and terminology.12. Calibration12.1 Prior to implementation of the ECN method, a labora-tory should demonstrate that acceptable precision and bias canbe obtained using a synthetic mixture of known composition(Calibration
35、 check sample).13. Procedure13.1 Bring the sample to room temperature.13.2 Check the chromatography performance to make surethat the column is properly resolving peaks.13.3 Inject an appropriate amount of sample into the instru-ment.13.4 Review the chromatographic data system result. Thenon-aromatic
36、s fraction includes all peaks up to ethylbenzene(except for the peaks assigned to benzene and toluene). Sumtogether all the non-aromatic peaks as a total area. The C9aromatics fraction includes cumene and all peaks emergingafter o-xylene, with exception of para-diethylbenzene (PDEB).Sum together all
37、 the C9aromatic peaks and report as a totalarea. If PDEB is included in the calibration, report PDEB.NOTE 1A poorly resolved peak, such as m-xylene, will often requirea tangent skim from the neighboring peak.13.5 See Figs. 1-4 for representative chromatograms.14. Calculation or Interpretation of Res
38、ults14.1 Using the ECN weight response factors listed in Table2, calculate the concentration of each component as follows:Ci5 100 3 Ai3 Ri!/(i5nnAi3 Ri! (1)where:Ci= concentration for component i, weight %,Ai= peak area of component i, andRi= ECN response factor for component i.15. Report15.1 Report
39、 individual impurities, total non-aromatics, andtotal C9aromatics, to the nearest 0.0001 %.15.2 For concentrations of impurities less than 0.0001 %,report as 0.0001 %, and consider as 0.0000 in summation ofimpurities.15.3 If necessary, report total xylenes to the nearest0.0001 %. It is the sum of m-
40、xylene, o-xylene, p-xylene, andethylbenzene by industry convention.15.4 Report the total impurities to the nearest 0.01 %.15.5 Report purity as “purity (by GC)” to the nearest0.01 %.16. Precision and Bias716.1 The precision of this test method is based on anintralaboratory study of Test Method D7504
41、 conducted in2008. One laboratory tested five different materials (twosamples of p-xylene, two samples of mixed xylene, and asingle toluene) for a number of impurities. Every test resultrepresents an individual determination. The laboratory reported20 replicate results for each analysis/material com
42、bination inorder to estimate the repeatability limits of the standard.Practice E691 was followed for the design and analysis of therepeatability data; the details are given in Research Report No.D161036.16.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not
43、equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.16.1.1.1 Repeatability limits are li
44、sted in Tables 3-7.16.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “R” valuefor that material; “R” is the interval representing the critical7Supporting data have been filed at ASTM International Headquarters and maybe obtained by request
45、ing Research Report RR:D16-1036.TABLE 2 Effective Carbon Number Response FactorsComponent Response Factor (Weight)ANon-aromatics 1.0000Benzene 0.9100Toleune 0.9200Ethylbenzene 0.9275p-Xylene 0.9275m-Xylene 0.9275o-Xylene 0.9275Cumene 0.9333p-diethylbenzene (PDEB) 0.9380AResponse factors are relative
46、 to n-heptane.TABLE 3 p-Xylene Sample 1AnalyteAverage(wt %)RepeatabilityStandardDeviationRepeatabilityLimitx SrrNon-aromatics 0.0272 0.0003 0.0008Benzene 0.0003 0.00001 0.00004Toluene 0.0044 0.00002 0.00006Ethylbenzene 0.0231 0.0001 0.0002m-Xlyene 0.0420 0.0001 0.0004o-Xylene 0.0150 0.00002 0.00004C
47、9aromatics 0.0079 0.0001 0.0003PDEB 0.0040 0.00003 0.00008p-Xlyene 99.8761 0.0003 0.0009D7504 0913difference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.16.1.2.1 Reproducibility limits cannot be determined formthe
48、current study.16.1.3 The above terms (repeatability and reproducibilitylimit) are used as specified in Practice E177.16.1.4 Any judgment in accordance with statements 16.1.1would have an approximate 95 % probability of being correct.16.2 BiasAt the time of the study, the test specimenschosen for ana
49、lysis were not accepted reference materialssuitable for determining the bias for this test method, thereforeno statement on bias is being made.16.3 The precision statement was determined through sta-tistical examination of all of the results submitted by onelaboratory, running twenty analyses, on up to five differentmaterials. These five materials were described as the follow-ing:Material 1: p-xyleneMaterial 2: p-xyleneMaterial 3: tolueneMaterial 4: mixed xyleneMaterial 5: mixed xylene16.4 To judge the equivalency of two test results, it isrecommended to
