ASTM_D_6445_-_99.pdf

Designation:D 6445 99An American National StandardStandard Test Method forSulfur in Gasoline by Energy-Dispersive X-ray FluorescenceSpectrometry1This standard is issued under the fixed designation D 6445;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the measurement of sulfur innonleaded gasoline and gasoline-oxygenate blends.The appli-cable concentration range is 48 to 1000 mg/kg sulfur.1.2 The values stated in SI units are to be regarded as thestandard.The preferred concentration units are mg/kg sulfur.1.3 This standard may involve hazardous materials,opera-tions,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.For specific precautionary statements,see Sections 5 and 7.2.Referenced Documents2.1 ASTM Standards:D 3120 Test Method for Trace Quantities of Sulfur in LightLiquid Petroleum Hydrocarbons by Oxidative Microcou-lometry2D 4057 Practice for Manual Sampling of Petroleum andPetroleum Products3D 4177 Practice for Automatic Sampling of Petroleum andPetroleum Products33.Summary of Test Method3.1 The sample is placed in the beam emitted from an X-raysource.The resultant excited characteristic X radiation ismeasured,and the accumulated count is compared with countsfrom previously prepared calibration standards to obtain thesulfur concentration in mg/kg.One group of calibration stan-dards is required to span the concentration 5 to 1000 mg/kgsulfur.4.Significance and Use4.1 This test method provides a means of quantifying sulfurcontent in gasoline.It can be referenced in specificationdocuments as a means to determine if the material meets thedesired sulfur content.It is a rapid and precise measurement oftotal sulfur in petroleum products with a minimum of samplepreparation.4.2 The quality of gasoline is related to the amount of sulfurpresent.Knowledge of sulfur concentration is necessary forprocessing purposes.There are also regulations promulgated infederal,state,and local agencies that restrict the amount ofsulfur present in gasoline as it affects performance character-istics and potential corrosion problems and emission levels.During combustion,the sulfur content in fuel affects SOxemissions,which degrade air quality.Certain jurisdictions mayrestrict the amount of sulfur in gasoline to prevent or limitpollution to the environment.5.Apparatus5.1 Energy-dispersive X-ray Fluorescence AnalyzerTheanalyzer needs to have sufficient sensitivity to measure theconcentration of sulfur at 500 mg/kg with a one standarddeviation value due to counting statistics no greater than 10mg/kg under optimized conditions.Any energy dispersiveX-ray fluorescence analyzer may be used if its design incor-porates,as a minimum,the following features:5.1.1 Source of X-ray ExcitationX-ray tube with energyabove 2.5 keV.NOTE1Operation of analyzers using X-ray tubes is to be conductedin accordance with the manufacturers safety instructions and federal stateand local regulations.5.1.2 Sample Cell,providing a sample depth of at least 4mm and equipped with replaceable X-ray transparent filmwindow.5.1.3 X-ray Detector,with a resolution value not to exceed800 eV at 2.3 keV.A gas filled proportional counter has beenfound suitable to use.5.1.4 Filters,or other means of discriminating betweensulfur Karadiation and other X rays.1This test method is under the jurisdiction of ASTM Committee D-2 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved July 10,1999.Published September 1999.2Annual Book of ASTM Standards,Vol 05.01.3Annual Book of ASTM Standards,Vol 05.02.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.5.1.5 Signal conditioning and data handling electronics thatinclude the functions of X-ray intensity counting,spectraloverlap corrections,and conversion of sulfur X-ray intensityinto mg/kg sulfur concentration.It is also imperative that theinstrument has the capability to monitor counts for at least oneenergy region distinct from the sulfur region to allow compen-sation for variations in spectral background(that is,calculationof net intensities).5.1.6 Display or Printer,that reads or prints out in mg/kg ormasspercent sulfur.6.Matrix Effects6.1 Matrix effects refer to changes in measured intensity ofsulfur caused by concentration variations of the elements in asample.These variations directly influence X-ray absorptionand change the measured intensity of each element.Forexample,performance