1、Designation: D7504 15Standard 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 totalnonaromatic hydrocarbons and mon
3、ocyclic aromatic hydrocar-bons in benzene, toluene, ethylbenzene, p-xylene, o-xylene,styrene and mixed xylenes by gas chromatography. The purityof benzene, toluene, ethylbenzene, p-xylene, o-xylene, styreneand mixed xylenes is also calculated. Similar test methods,using the internal standard calibra
4、tion technique and theexternal standard calibration technique, are Test MethodsD2360, D3797, D4492, D5060, D5135, D5917, and D6563respectively.1.2 A small amount of benzene in toluene, ethylbenzene,p-xylene, o-xylene, styrene and mixed xylenes may not bedistinguished from the non-aromatics and the c
5、oncentrationsare determined as a composite (see 6.1).1.3 The limit of detection (LOD) is 0.0002 wt % and limitof quantitation (LOQ) is 0.0006 wt % for impurities in toluene,mixed xylenes, p-xylene, o-xylene, ethylbenzene, benzene, andstyrene.1.4 In determining the conformance of the test results usi
6、ngthis 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 measurement are included in thisstandard.1.6 This standard does not purport to address
7、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 prior to use.2. Referenced Documents2.1 ASTM Standards:2D841 Specification
8、 for Nitration Grade TolueneD1555M Test Method for Calculation of Volume and Weightof Industrial Aromatic Hydrocarbons and CyclohexaneMetricD2360 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas ChromatographyD3437 Practice for Sampling and Handling Liquid CyclicProductsD37
9、97 Test Method for Analysis of o-Xylene by Gas Chro-matography (Withdrawn 2014)3D4492 Test Method for Analysis of Benzene by Gas Chro-matographyD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD5060 Test Method for Determining Impurities in High-Purity Ethylbenzene by Gas Chromatograph
10、yD5135 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 Impurities in MonocyclicAromatic Hydrocarbons by Gas Chromatography andExternal CalibrationD6229 Test
11、 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 Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice
12、for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibili
13、ty ofSubcommittee D16.01 on Benzene, Toluene, Xylenes, Cyclohexane and TheirDerivatives.Current edition approved July 1, 2015. Published July 2015. Originally approvedin 2009. Last previous edition approved in 2012 as D7504 12. DOI: 10.1520/D7504-15.2For referenced ASTM standards, visit the ASTM web
14、site, 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.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes secti
15、on appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relation-shipsE691 Practice for Conducting an Inter
16、laboratory Study toDetermine 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 and1910.120043. Terminology3.1 See Terminology D4790 for definitions of terms used
17、 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 factors. The co
18、ncentration 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-xylene, o-xylene, ethy
19、lbenzene, 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 containing 1 to 10 carbons
20、 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 beabsolute.6. Int
21、erferences6.1 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 be determined, an
22、alternate 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 analyzed, respectively
23、.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 resolutionrequireme
24、nts. 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 flameionization detecto
25、r 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 major compo-nent.
26、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 automatic samplein
27、jection devise is highly recommended.7.5 Syringechromatographic, capable of delivering appro-priate L volumes.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,
28、 D. E., “Calculation of Flame Ionization DetectorRelative Response Factors Using the Effective Carbon Number Concept,” Journalof Chromatographic Science, Vol. 23, August 1985, pp. 333339.TABLE 1 Recommended Method ParametersInlet SplitTemperature, C 270Column:Tubing fused silicaLength, m 60Internal
29、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 ra
30、tio 100:1Sample size, L 0.6Detector: flame ionizationTemperature, C 300Analysis time, min 38D7504 1528. Reagents and Materials8.1 Purity of ReagentReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the
31、 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 Detector Gases99.999 % Pure. Oxygen in carrier gas less than 1 ppm, lessthan 0.5 ppm
32、 is preferred. Purify carrier, makeup and detectorgases to remove oxygen, water, and hydrocarbons.8.3 Air for the FID should contain less than 0.1 ppm totalhydrocarbon.8.4 Calibration Check Standard. This standard may bepurchased if desired.9. Hazards9.1 Consult current OSHA regulations, suppliers S
33、afetyData Sheets, and local regulations for all materials used in thistest method.10. Sampling10.1 Sample the material in accordance with PracticeD3437.11. Preparation of Apparatus11.1 Follow manufacturers instructions for mounting andconditioning the column into the chromatograph and adjustingthe i
34、nstrument to the conditions described in Table 1, allowingsufficient time for the equipment to reach equilibrium. SeePractices 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
35、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 temperature.13.2 Check the chromatography performance to make surethat the column is properly resolving peaks.13.3
36、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 up to ethylbenzene except for the peaks assigned tobenzene and toluene. Sum together all the non-aromatic peaks
37、as 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 poorly resolved peak, such as p-xylene from high purityethylbenzene or m-xylene from high purity p-xylene, will of
38、ten require atangent skim from the neighboring peak.13.5 See Figs. 1-8 for representative chromatograms.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see A
39、nalar 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 2 Effective Carbon Number Response Factors andDensityComponentECNResponse FactorADensity at 20CNon Aromatic
40、s 1.0000 0.7255 (average)BBenzene 0.9100 0.8780CToluene 0.9200 0.8658CEthylbenzene 0.9275 0.8658Cp-Xylene 0.9275 0.8597Cm-Xylene 0.9275 0.8630Co-Xylene 0.9275 0.8786CCumene 0.9333 0.8605C1,4-Dioxane 3.0800 1.0329DC9+Aromatics 0.9333 0.8715EaverageStyrene 0.91 0.9048CC10Aromatics 0.938 0.8694Eaverage
41、p-diethylbenzene(PDEB)0.938 0.8620EAResponse factors are relative to n-heptane.BDS#4APhysical Constants of Hydrocarbons C1through C10, ASTM, 1971.Average of hexane, methylcyclopentane, methylcyclohexane, heptane, andethylcyclopentane.CTest Method D1555M.DKeith, L. H., Walters, D B., Compendium of Sa
42、fety Data Sheets for Research andIndustrial Chemicals, Part II, VCH Publishers, Deerfield Beach, p. 726, 1985.ECRC Handbook of Chemistry and Physics, David R. Lide, 88th Ed., 20072008.D7504 153FIG. 1 Typical Chromatogram of Synthetic BlendD7504 154FIG. 2 Typical Chromatogram of TolueneD7504 155FIG.
43、3 Typical Chromatogram of Specification D5211, XylenesD7504 156FIG. 4 Typical Chromatogram of Specification D5136, p-XyleneD7504 15714. Calculation or Interpretation of Results14.1 Using the ECN weight response factors listed in Table2, calculate the concentration of each component as follows:Ci5 10
44、0 3 Ai3 Ri!/(i51nAi3 Ri! (1)where:Ci= concentration for component i, weight %,Ai= peak area of component i, andRi= ECN response factor for component i.14.2 Calculate the volume percent concentration of eachcomponent using the density in Table 2 as follows:Vi5 100 3 Ci/Di!/(i51nCi/Di! (2)where:Vi= ca
45、lculated vol % concentration of component i,Ci= calculated wt % concentration of component i from14.1, andDi= density of component i.15. Report15.1 Report individual impurities and total non-aromatics,to the nearest 0.0001 %.FIG. 5 Typical Chromatogram of BenzeneFIG. 6 Typical Chromatogram of o-Xyle
46、neD7504 15815.1.1 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 convention.15.2 Fo
47、r 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 Bias716.1 An ILS was conducted which included 14
48、 laboratoriesanalyzing 7 different materials. Each material was at 4 differentlevels and each level was analyzed 3 times. Practice E691 wasfollowed for the design and analysis of the data; the details aregiven in a Research Report.7The outliers for para-xylene wereidentified and removed using the t
49、test.16.1.1 The para-xylene samples were prepared by purifyingpara-xylene. Level 1 was the purified material. Levels 2, 3, and7Supporting data pending being filed at ASTM International Headquarters.FIG. 7 Typical Chromatogram of EthylbenzeneFIG. 8 Typical Chromatogram of StyreneD7504 1594 had increasing amounts of the concentrated impurities fromthe purification process added.16.1.2 The benzene, ethylbenzene, mixed xylenes, ortho-xylene, styrene, and toluene had known amounts added tolevels 2, 3, and 4. See 16.4 for levels and recovery.16.2 R
