ASTM_D_7536_-_09.pdf

Designation:D753609Standard Test Method forChlorine in Aromatics by Monochromatic WavelengthDispersive X-ray Fluorescence Spectrometry1This standard is issued under the fixed designation D7536;the number immediately following the designation indicates the year oforiginal adoption or,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 chlorine bymonochromatic,wavelength-dispersive X-ray fluorescence(MWDXRF)spectrometry in aromatic hydrocarbons,theirderivatives,and related chemicals.1.2 This test method is applicable to samples with chlorineconcentrations from 0.5 mg/kg to 15 mg/kg.Higher chlorineconcentrations can be determined by quantitatively diluting thesample with a suitable solvent.In a preliminary robustnessstudy,the limit of detection was estimated to be 0.06 mg/kg.1.3 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 E29.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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 prior to use.For specific hazardinformation,see Section 9.2.Referenced Documents2.1 ASTM Standards:2D3437 Practice for Sampling and Handling Liquid CyclicProductsD4790 Terminology of Aromatic Hydrocarbons and RelatedChemicalsD6809 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 Specifications2.2 Other Documents:3OSHA Regulations,29 CFR paragraphs 1910.1000 and1910.12003.Terminology3.1 See Terminology D4790 for definitions of terms used inthis test method.4.Summary of Test Method4.1 A monochromatic X-ray beam with a wavelength suit-able to excite the K-shell electrons of chlorine is focused ontoa test specimen contained in a sample cell(see Fig.1).Thefluorescent K radiation at 0.473 nm(4.73)emitted bychlorine is collected by a fixed monochromator(analyzer).Theintensity(counts per second)of the chlorine X-rays is mea-sured using a suitable detector and converted to the concen-tration of chlorine(mg/kg)in a test specimen using a calibra-tion equation.Excitation by monochromatic X-rays reducesbackground,simplifies matrix correction and increases thesignal/background ratio compared to polychromatic excitationused in conventional WDXRF techniques.45.Significance and Use5.1 This test method provides for the precise measurementof the chlorine content of aromatics with minimal samplepreparation and analyst involvement.The typical time for eachanalysis is five or ten minutes.5.2 Knowledge of the chlorine content of aromatics isimportant for process control as well as the prediction andcontrol of operational problems such as unit corrosion andcatalyst poisoning,and in the blending of products to com-modity specifications.1This test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.04 on Instrumental Analysis.Current edition approved Sept.1,2009.Published September 2009.DOI:10.1520/D7536-09.2For 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.3Available 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.4Bertin,E.P.,Principles and Practices of X-ray Spectrometric Analysis,PlenumPress,New York,1975,pp.115-118.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3 Various federal,state,and local agencies regulate thechlorine content of some petroleum products,including aro-matics.Unbiased and precise determination of chlorine inaromatics is critical to compliance with regulatory standards.5.4 When the elemental composition of the samples differsignificantly from the calibration standards used to prepare thecalibration curve,the cautions and recommendation in Section6 should be carefully observed.6.Interferences6.1 Differences between the elemental composition of testsamples and the calibration standards can result in biasedchlorine determinations.For aromatics within the scope of thistest method,matrix correction can be avoided with a properchoice of calibrants.To minimize any bias in the results,usecalibration stand