1、Designation: D 7504 09Standard Test Method forTrace Impurities in Monocyclic Aromatic Hydrocarbons byGas Chromatography and Effective Carbon Number1This standard is issued under the fixed designation D 7504; the number immediately following the designation indicates the year oforiginal adoption or,
2、in 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. Scope1.1 This test method covers the determination of the totalnonaromatic hydrocarbons an
3、d 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 and the external stan-dard calibration technique, are
4、Test Method D 2360 andD 5917 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 to2.5000 weight %. The limit of detection is 0.00003 weight %and the limit of quantitation
5、 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 through 10 carbon atoms (benzene through C10aromati
6、cs)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 value or a calculated value shall berounded off “t
7、o 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 included in thisstandard.1.6 This standard does not
8、 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 prior to use.2. Referenced Documents2.1 ASTM Standards
9、:2D 841 Specification for Nitration Grade TolueneD 2360 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas ChromatographyD 3437 Practice for Sampling and Handling Liquid CyclicProductsD 4534 Test Method for Benzene Content of Cyclic Prod-ucts by Gas Chromatography3D 4790 Term
10、inology of Aromatic Hydrocarbons and Re-lated ChemicalsD 5136 Specification for High Purity p-XyleneD 5211 Specification for Xylenes for p-Xylene FeedstockD 5917 Test Method for Trace Impurities in MonocyclicAromatic Hydrocarbons by Gas Chromatography andExternal CalibrationD 6809 Guide for Quality
11、Control and Quality AssuranceProcedures for Aromatic Hydrocarbons and Related Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 260 Practice for Packed Column Gas Chr
12、omatographyE 355 Practice for Gas Chromatography Terms and Rela-tionshipsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 1510 Practice for Installing Fused Silica Open TubularCapillary Columns in Gas Chromatographs2.2 Other Document:1This test metho
13、d 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 February 2009.2For referenced ASTM s
14、tandards, 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 historical standard is referencedon w
15、ww.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 D 4790 for definitions of terms used inthis test method.4. Summary of Test Metho
16、d4.1 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 iscalculated b
17、ased 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 used as chemical intermediates andsolvents is often req
18、uired. 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, ethylbenzene (EB), xylenes, and aromatichydrocarbons containin
19、g 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 xylenes and p-xylene, it may bedifficult to resolve benzene
20、 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 D 4534must be selected to ensure an accurate assessment of thebenzene concentration.6.2 Complete se
21、paration 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 required.7.2 ColumnsThe choice of column is bas
22、ed 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.7.3 Gas ChromatographAny instrument having
23、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 eitherthe detector or the electronic integration f
24、or 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 repeat-ably injected into the gas chromatogr
25、aph.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 indicated, it is intended thatall reagents shall
26、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 detector gases 99.999 %pure. Oxygen in carrier g
27、as 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 standard may bepurchased if desired.4Available from U.S. Go
28、vernment 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 the Effective Carbon Number Concept,” Journalof Chro
29、matographic 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, see Analar Standards for LaboratoryChemicals, BDH Ltd.,
30、 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 diameter, mm 0.32Stationary phase crosslinked poly
31、ethyleneglycolFilm 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 hydrocarbonSplit ratio 100:1Sample size, L 0.6Detector: flame ioni
32、zationTemperature, C 300Analysis time, min 38D75040929. 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 PracticeD 3437.11. Preparation of Apparat
33、us11.1 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 E 260, E 355, and E 1510 for additional information
34、on gas 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 sample).13. Procedure13.1 Bring the sampl
35、e 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 includes all peaks up to ethylbenzene
36、(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 C9aromatic peaks and report as a totalarea.
37、 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 Results14.1 Using the ECN weight response factors l
38、isted 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, total non-aromatics, and
39、total 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-xylene, o-xylene, p-xylene, andethylbenzene by i
40、ndustry 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 D 7504 conducted in2008. One laboratory tested five d
41、ifferent 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 combination inorder to estimate the repeatability
42、limits of the standard.Practice E 691 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 equivalent if theydiffer by more than the “r”
43、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 listed in Tables 3-7.16.1.2 Reproducibility Limi
44、t (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 requesting Research Report RR: D161036.TABLE 2 Effect
45、ive 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 to n-heptane.TABLE 3 p-Xylene Sample 1Analyte
46、Average(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 0.00004C9aromatics 0.0079 0.0001 0.0003PDEB 0.0040 0.0
47、0003 0.00008p-Xlyene 99.8761 0.0003 0.0009D7504093difference 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 current study.16.1.3 The above terms (repeatabil
48、ity and reproducibilitylimit) are used as specified in Practice E 177.16.1.4 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 materialssuit
49、able 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 choose the material closest in characteristicsto the
