1、Designation: D7504 10Standard 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, in
2、 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.1. Scope*1.1 This test method covers the determination of the totalnonaromatic hydrocarbons and
3、 trace monocyclic aromatichydrocarbons in toluene, mixed xylenes, p-xylene, o-xylene,ethylbenzene, and benzene by gas chromatography. The purityof toluene, mixed xylenes, p-xylene, o-xylene, ethylbenzene,or benzene can also be calculated. Similar test methods, usingthe internal standard calibration
4、technique and the externalstandard calibration technique, are Test Methods D2360,D3797, D4492, D5060, D5917, and D6563 respectively.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
5、to2.5000 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 through 10 carbon atoms (benzene through C10aromatics
6、)can be detected by this test method at individual concentrationsranging from 0.0001 to 2.5000 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
7、values stated in SI units are to be regarded asstandard. No other units of measurement 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
8、 safety and health practices and determine the applica-bility of regulatory limitations prior 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
9、for Sampling and Handling Liquid CyclicProductsD3797 Test Method for Analysis of o-Xylene by GasChromatographyD4492 Test Method for Analysis of Benzene by Gas Chro-matographyD4534 Test Method for Benzene Content of Cyclic Prod-ucts by Gas Chromatography3D4790 Terminology ofAromatic Hydrocarbons and
10、RelatedChemicalsD5060 Test Method for Determining Impurities in High-Purity Ethylbenzene by Gas ChromatographyD5136 Specification for High Purity p-XyleneD5211 Specification for Xylenes for p-Xylene FeedstockD5917 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas Chromatogra
11、phy andExternal CalibrationD6563 Test Method for Benzene, Toluene, Xylene (BTX)Concentrates Analysis by Gas ChromatographyD6809 Guide for Quality Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine
12、 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-tionships1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydroca
13、rbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.01 on Benzene, Toluene, Xylenes, Cyclohexane and TheirDerivatives.Current edition approved July 15, 2010. Published October 2010. Originallyapproved in 2009. Last previous edition approved in 2009 as D7504 - 091. DOI:10.
14、1520/D7504-10.2For 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 approved version of this h
15、istorical standard is referencedon www.astm.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.E691 Practice for Conducting an Interlaboratory Study toDetermine the P
16、recision of a Test MethodE1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and1910.120043. Terminology3.1 See Terminology D4790 for definitions of terms used inthis test method.4. Summary of
17、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 factors. The concentration of each component isca
18、lculated 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, p-xylene, o-xylene, ethylbenzene, and benzene usedas chemi
19、cal intermediates and solvents is often required. Thistest method is suitable for setting specifications and for use asan internal quality control tool where these products areproduced or are used. Typical impurities are: alkanes contain-ing 1 to 10 carbons atoms, benzene, toluene, ethylbenzene(EB),
20、 xylenes, and aromatic hydrocarbons containing ninecarbon 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 xylenes and p-x
21、ylene, 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 assessment
22、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 system is requ
23、ired.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 ofdispute.
24、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 of eithert
25、he 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 precisely and r
26、epeat-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 otherwise indica
27、ted, 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 and detec
28、tor gases 99.999 %pure. Oxygen in carrier gas less than 1 ppm, less than 0.5 ppm4Available 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
29、Ionization DetectorRelative Response Factors Using 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 reage
30、nts notlisted by the American Chemical Society, see 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,
31、 C 270Column:Tubing fused silicaLength, m 60Internal 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 ve
32、locity, cm/s at 145C 20 helium or 45 hydrogenSplit ratio 100:1Sample size, L 0.6Detector: flame ionizationTemperature, C 300Analysis time, min 38D7504 102is preferred. Purify carrier, makeup and detector gases toremove oxygen, water, and hydrocarbons.8.3 Air for the FID should contain less than 0.1
33、ppm totalhydrocarbon.8.4 Calibration Check Standard. This standard may bepurchased if desired.9. 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 accordance with
34、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 E260, E355,
35、 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 check samp
36、le).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-aromatics fraction
37、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 the C9arom
38、atic peaks and report as a totalarea if required by specification. If PDEB is included in thecalibration, report PDEB.NOTE 1A poorly resolved peak, such as m-xylene, will often requirea tangent skim from the neighboring peak.13.5 See Figs. 1-7 for representative chromatograms.14. Calculation or Inte
39、rpretation of Results14.1 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.
40、Report15.1 Report individual impurities, total non-aromatics, andtotal C9aromatics, if required by specification, to the nearest0.0001 %.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 xylen
41、es to the nearest0.0001 %. It is the sum of m-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 Bias7,816.1 The precision of this test method is based
42、 on anintralaboratory study of Test Method D7504 conducted in 2008and 2010. One laboratory tested eleven different materials (twosamples of p-xylene, two samples of mixed xylene, and asingle toluene, two samples of o-xylene, two samples ofethylbenzene, and two samples of benzene) for a number ofimpu
43、rities. Every test result represents an individual determi-nation. The laboratory reported 20 replicate results for eachanalysis/material combination in order to estimate the repeat-ability limits of the standard. Practice E691 was followed forthe design and analysis of the repeatability data; the d
44、etails aregiven in Research Report No. D161036 and D161040.16.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two testres
45、ults 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 listed in Tables 3-13.7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-
46、1036.8Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1040.TABLE 2 Effective Carbon Number Response FactorsComponent Response Factor (Weight)ANon-aromatics 1.0000Benzene 0.9100Toleune 0.9200Ethylbenzene 0.9275p-Xylene 0.9275m
47、-Xylene 0.9275o-Xylene 0.9275Cumene 0.9333C9aromatics 0.9333Styrene 0.91C10aromatics 0.938p-diethylbenzene (PDEB) 0.93801,4dioxane 3.08AResponse factors are relative to n-heptane.D7504 10316.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “
48、R” valuefor that material; “R” is the interval representing the criticaldifference 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 fromthe current study.16.1.3 The a
49、bove 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 analysis 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 ana
