1、Designation: D7504 11Standard 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, benzene, and styrene by gas chromatography.The purity of toluene, mixed xylenes, p-xylene, o-xylene,ethylbenzene, benzene, and stryene can also be calculated.Similar test methods, using the internal st
4、andard calibrationtechnique and the external standard calibration technique, areTest Methods D2360, D3797, D4492, D5060, D5135, D5917,and D6563 respectively.1.2 Total aliphatic hydrocarbons containing 1 through 10carbon atoms (methane through decanes) can be detected bythis test method at concentrat
5、ions ranging from 0.0001 to2.5000 weight %.1.2.1 A small amount of benzene in toluene, mixed xylenes,p-xylene, o-xylene, ethylbenzene, or styrene may not bedistinguished from the non-aromatics and the concentrationsare determined as a composite (see 6.1).1.3 Monocyclic aromatic hydrocarbon impuritie
6、s containing6 through 10 carbon atoms (benzene through C10aromatics)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
7、 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 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 there
8、sponsibility of the user of this standard to establish appro-priate 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 M
9、onocyclicAromatic Hydrocarbons by Gas ChromatographyD3437 Practice for Sampling and Handling Liquid CyclicProductsD3797 Test Method for Analysis of o-Xylene by GasChromatographyD4492 Test Method for Analysis of Benzene by Gas Chro-matographyD4790 Terminology ofAromatic Hydrocarbons and RelatedChemic
10、alsD5060 Test Method for Determining Impurities in High-Purity Ethylbenzene by Gas ChromatographyD5135 Test Method for Analysis of Styrene by CapillaryGas ChromatographyD5136 Specification for High Purity p-XyleneD5211 Specification for Xylenes for p-Xylene FeedstockD5917 Test Method for Trace Impur
11、ities in MonocyclicAromatic Hydrocarbons by Gas Chromatography andExternal CalibrationD6229 Test Method for Trace Benzene in HydrocarbonSolvents by Capillary Gas ChromatographyD6563 Test Method for Benzene, Toluene, Xylene (BTX)Concentrates Analysis by Gas ChromatographyD6809 Guide for Quality Contr
12、ol 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 MethodsE260 Practice for Packed Column Gas Chromatogr
13、aphyE355 Practice for Gas Chromatography Terms and Rela-tionshipsE691 Practice for Conducting an Interlaboratory Study to1This 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,
14、Toluene, Xylenes, Cyclohexane and TheirDerivatives.Current edition approved June 1, 2011. Published August 2011. Originallyapproved in 2009. Last previous edition approved in 2010 as D7504 - 10. DOI:10.1520/D7504-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
15、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
16、ocken, PA 19428-2959, United States.Determine the Precision 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 and1910.120033. Terminology3.1 See Terminology D4790 for definiti
17、ons of 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)4respons
18、e factors. 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, p-xylen
19、e, o-xylene, ethylbenzene, benzene, and sty-rene used as chemical intermediates and solvents is oftenrequired. This test method is suitable for setting specificationsand for use as an internal quality control tool where theseproducts are produced or are used. Typical impurities are:alkanes containin
20、g 1 to 10 carbons atoms, benzene, toluene,ethylbenzene (EB), xylenes, and aromatic hydrocarbons con-taining nine carbon atoms or more.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
21、beabsolute.6. Interferences6.1 In some cases for toluene, mixed xylenes, p-xylene,o-xylene, ethylbenzene and styrene, it may be difficult toresolve benzene from the nonaromatic hydrocarbons. There-fore the concentrations are determined as a composite. In theevent that the benzene concentration must
22、be determined, analternate method such as Test Method D6229 must be selectedto ensure an accurate assessment of the benzene concentration.6.2 The complete separation of p-xylene from ethylbenzene,or ethylbenzene and m-xylene from p-xylene can be difficultwhen either ethylbenzene or p-xylene is analy
23、zed, respecively.The separation can be considered adequate if the distance fromthe baseline to the valley between the two peaks is not greaterthan 50 % of the peak height of lower of the two peaks.7. Apparatus7.1 Chromatographic data system is required.7.2 ColumnsThe choice of column is based on res
24、olutionrequirements. 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.7.3 Gas ChromatographAny instrument having a flameio
25、nization 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 eitherthe detector or the electronic integration for the ma
26、jor 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 repeat-ably injected into the gas chromatograph.An au
27、tomatic 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 indicated, it is intended thatall reagents shall conform t
28、o the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society,5where such specifications are available. Reagents with anestablish purity greater than ACS reagent grade may be used.8.2 Carrier Gas, Makeup Gas and Detector Gases99.999 % pure. Oxygen in carrier gas less t
29、han 1 ppm, less than3Available 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.4Scanlon, J. T. and Willis, D. E., “Calculation of Flame Ionization DetectorRelative Response Factors Using the Effec
30、tive Carbon Number Concept,” Journalof Chromatographic Science, Vol. 23, August 1985, pp. 333339.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar S
31、tandards 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 60Internal diamete
32、r, 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 ratio 100
33、:1Sample size, L 0.6Detector: flame ionizationTemperature, C 300Analysis time, min 38D7504 1120.5 ppm is preferred. Purify carrier, makeup and detector gasesto remove oxygen, water, and hydrocarbons.8.3 Air for the FID should contain less than 0.1 ppm totalhydrocarbon.8.4 Calibration Check Standard.
34、 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 PracticeD3437.11. Preparation of Apparatus11.1 Follo
35、w 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, and E1510 for additional information ongas chromato
36、graphy 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 sample).13. Procedure13.1 Bring the sample to room tempe
37、rature.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. Mea-sure the area of all peaks. The non-aromatics fraction includesall peaks u
38、p to ethylbenzene except for the peaks assigned tobenzene and toluene. Sum together all the non-aromatic peaksas a total area. When either benzene or toluene is analyzed and1,4-dioxane is required to be reported, the non-aromaticfraction does not include the peak assigned to 1,4-dioxane.NOTE 1A poor
39、ly resolved peak, such as p-xylene from high purityethylbenzene or m-xylene from high purity p-xylene, will often require atangent skim from the neighboring peak.13.5 See Figs. 1-8 for representative chromatograms.14. Calculation or Interpretation of Results14.1 Using the ECN weight response factors
40、 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 individual impurities and total non-aromatics
41、,to the nearest 0.0001 %.15.1.1 If required, report total C9+aromatics to the nearest0.0001 %. It is the sum of cumene and all peaks emerging aftero-xylene.15.1.2 If required, report total xylenes to the nearest0.0001 %. It is the sum of m-xylene, o-xylene, p-xylene, andethylbenzene by industry conv
42、ention.15.2 For concentrations of impurities less than 0.0001 %,report as 0.0001 %, and consider as 0.0000 in summation ofimpurities.15.3 Report the total impurities to the nearest 0.01 %.15.4 Report purity as “purity (by GC)” to the nearest0.01 %.16. Precision and Bias6,7,816.1 The precision of thi
43、s test method is based on anintralaboratory study of Test Method D7504 conducted in 2008and 2010. One laboratory tested thirteen different materials(two samples of p-xylene, two samples of mixed xylene, and asingle toluene, two samples of o-xylene, two samples ofethylbenzene, and two samples of benz
44、ene, and two samples ofstyrene) for a number of impurities. Every test result representsan individual determination. The laboratory reported 20 repli-cate results for each analysis/material combination in order toestimate the repeatability limits of the standard. Practice E691was followed for the de
45、sign and analysis of the repeatabilitydata; the details are given in Research Report No. D161036,D161040, and D161043.16.1.1 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”istheinterv
46、al representing the critical difference between two test6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1036.7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Repor
47、t RR:D16-1040.8Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D16-1043.TABLE 2 Effective Carbon Number Response FactorsComponent Response Factor (Weight)ANon-aromatics 1.0000Benzene 0.9100Toleune 0.9200Ethylbenzene 0.9275p-Xylen
48、e 0.9275m-Xylene 0.9275o-Xylene 0.9275Cumene 0.9333C9aromatics 0.9333Styrene 0.91C10aromatics 0.938p-diethylbenzene (PDEB) 0.93801,4-dioxane 3.08Ethyltoluene 0.93332-propenylbenzene 0.9178a methylstyrene 0.9178Phenylethyne 0.8925AResponse factors are relative to n-heptane.D7504 113results for the sa
49、me 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 3-15.16.1.2 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 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.
