ASTM D7212-2013(2018) 1875 Standard Test Method for Low Sulfur in Automotive Fuels by Energy-Dispersive X-ray Fluorescence Spectrometry Using a Low-Background Proportional Counter.pdf

1、Designation: D7212 13 (Reapproved 2018)Standard Test Method forLow Sulfur in Automotive Fuels by Energy-Dispersive X-rayFluorescence Spectrometry Using a Low-BackgroundProportional Counter1This standard is issued under the fixed designation D7212; the number immediately following the designation ind

2、icates 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 specifies an energy-disp

3、ersive X-rayfluorescence (EDXRF) method for the determination of thetotal sulfur content of automotive fuels with a concentrationrange from 7 mg/kg to 50 mg/kg.1.1.1 The pooled limit of quantitation of this test method asobtained by statistical analysis of interlaboratory test results is7 mg kg sulf

4、ur.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 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

5、-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDev

6、elopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D4045 Test Method for Sulfur in Petroleum Products byHydrogenolysis and Rateometric ColorimetryD4057 Practice

7、for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6300 Practice for Determination

8、of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6792 Practice for Quality Management Systems in Petro-leum Products, Liquid Fuels, and Lubricants TestingLaboratoriesD7343 Practice for Optimization, Sample Handling,Calibration, and Validation of X-ray Fluorescen

9、ce Spec-trometry Methods for Elemental Analysis of PetroleumProducts and LubricantsE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 low background proportional counter, nan X-raypr

10、oportional counter that can suppress the noise generatedwhen incident X rays are absorbed near the wall with resultingincomplete charge collection.3.1.1.1 DiscussionAn electrode shield close to the walldetects incomplete charge collection and associated electronicdetection circuitry rejects those ev

11、ents. In comparison toconventional proportional counters, this gives lower spectralbackground and a lower limit of detection.4. Summary of Test Method4.1 The sample is placed in the beam emitted from an X-raysource with titanium target and primary filtration so thatexcitation is by essentially monoc

12、hromatic radiation of4.51 keV and virtually no background at 2.3 keV. A lowbackground proportional counter measures the intensity of thefluorescent sulfur K series intensity and argon K series inten-sity (from residual air) and the accumulated counts are com-pared with counts from previously prepare

13、d calibration stan-dards to obtain the sulfur concentration in mg/kg. If chlorine isexpected to be present in some samples then other regions ofthe spectrum must be measured to provide compensation for1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuel

14、s, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved July 1, 2018. Published August 2018. Originallyapproved in 2006. Last previous edition approved in 2013 as D7212 13. DOI:10.1520/D7212-13R18.2For referenced ASTM standards, visit t

15、he 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.

16、United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barr

17、iers to Trade (TBT) Committee.1spectral overlap. One group of calibration standards is requiredto span the concentration range from 0 mg kg to 150 mg kgsulfur.NOTE 1Operation of analyzers using X-ray tubes is to be conductedin accordance with the manufacturers safety instructions and federal,state,

18、and local regulations governing the use of ionizing radiation.4.2 Practice D7343 should be consulted regarding standardoperating protocols in XRF analysis.5. Significance and Use5.1 This test method determines total sulfur in automotivefuels with a typical analysis time around 10 min per sample.5.2

19、The quality of automotive fuel is related to the amountof sulfur present. Knowledge of sulfur level is necessary forprocessing purposes.5.3 Sulfur level in automotive fuels affects performancecharacteristics and air quality. Federal, state, and local agenciesregulate the level of sulfur in fuel deli

20、vered at the pump.5.4 This test method can be referenced in specificationdocuments to determine if the material meets the desired sulfurcontent.5.5 If this test method is applied to petroleum matrices withsignificantly different composition to those used in the inter-laboratory precision study, then

21、 the caution and recommenda-tions in Section 6 should be observed when interpreting theresults.6. Interferences6.1 Spectral interferences result when some sample compo-nent element or elements emit X rays that the detector cannotresolve from sulfur X-ray emission. Overlapping peak lines arethe resul

22、t of this. This overlapping effect may be by lead alkyls,silicon, phosphorus, calcium, potassium, and halides if theiraggregate concentration is more than 10 mg kg. The mostlikely interference is chlorine that has been found in biodieselderived from recycled waste vegetable oil.6.2 The presence of o

23、xygenates or water may alter thesensitivity for sulfur.6.3 Follow the manufacturers operating guide to compen-sate for the interferences.7. Apparatus7.1 Energy-dispersive X-ray Fluorescence AnalyzerAnyenergy dispersive X-ray fluorescence analyzer may be used ifits design incorporates, as a minimum t

24、he following features:37.1.1 Source of X-ray Excitation, X-ray source with titaniumtarget and primary filtration so that excitation is by essentiallymonochromatic radiation of 4.51 keV.7.1.2 Low Background Proportional Counter (see 3.1.1),with sensitivity at 2.3 keV.47.1.3 Multi-channel Analyzer, wi

25、th a channel width of 10eVor less, covering the energy range from 0 keV to 10 keV.7.1.4 Signal Conditioning and Data Handling Electronics,that include the functions of X-ray intensity counting, aminimum of four energy regions (to correct for background Xrays and spectral overlap), spectral overlap c

26、orrections, andconversions of sulfur X-ray intensity into sulfur concentration.7.1.5 Display or Printer, that reads out in mg/kg sulfur.7.1.6 Removable Sample Cell, providing a sample depth ofat least 4 mm and equipped with a replaceable X-ray transpar-ent plastic film window.7.1.7 Helium Purged Opt

27、ical Path, to maximize sensitivityand minimize spectral overlap from argon in air. The heliumshall be at least 99.9 % purity.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the sp

28、ecifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8

29、.2 Di-n Butyl Sulfide (DBS), a high purity standard withcertified analysis for sulfur content. Use the certified sulfurcontent when calculating the exact concentrations of thecalibration standards. (WarningDi-n-butyl sulfide is flam-mable and toxic).8.3 Mineral Oil, White (MOW), with sulfur content

30、less than0.2 mg kg as certified by a suitable analytical method, like TestMethod D4045.8.4 X-ray Transparent Film, any film that resists attack bythe sample, is free of sulfur and other interfering elements (see6.1), and is sufficiently X-ray transparent may be used.NOTE 2Polycarbonate with thicknes

31、s of 5 or 6 m most closelymatches these requirements and eight of nine participants in the interlabo-ratory study6used one of these films, while the other laboratory used 3 mpolyester.8.4.1 Samples of high aromatic content may dissolve poly-carbonate film and polypropylene has a tendency to absorbso

32、me hydrocarbons and may stretch during a long measure-ment time.3The sole source of supply of the apparatus known to the committee at this timeis the Twin-X ULS from Oxford Instruments Analytical, Halifax Road, HighWycombe, Bucks, HP12 3SE, England. If you are aware of alternative suppliers,please p

33、rovide this information to ASTM International Headquarters. Your com-ments will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.4The low background proportional counter is covered by a pending patent.Interested parties are invited to submit info

34、rmation regarding the identification of analternative(s) to this patent-pending item toASTM International Headquarters. Yourcomments will receive careful consideration at a meeting of the responsibletechnical committee,1which you may attend.5Reagent Chemicals, American Chemical Society Specification

35、s, AmericanChemical Society, Washington DC. For suggestions on testing of reagents not listedby the American Chemical Society, see Annual Standards for Laboratory , BDHLtd., Poole Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S Pharmacopeial Convention, Inc. (USPC), Rockv

36、ille, MD.6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1587. ContactASTM CustomerService at serviceastm.org.D7212 13 (2018)2NOTE 3One laboratory has shown that polycarbonate resists a mixtureof 25 % by mass isooctane and 7

37、5 % by mass toluene for 80 min.8.4.2 In these cases high purity polyester is acceptable, butoverall, polycarbonate offers the best combination of spectralpurity and resistance to stretching. Other materials may be usedfor X-ray windows, provided that they do not contain anyelemental impurities and m

38、atch the listed films for X-raytransmission.8.5 Sample Cells, resistant to sample attack and meet thegeometry requirements of spectrometer.8.6 Calibration Check Samples, portions of one or moreautomotive fuel standards of known sulfur content and not usedin the generation of the calibration line. Th

39、e check samplesshall be used to determine the accuracy of the initial calibration(see 11.3).8.7 Quality Control (QC) Samples, preferably portions ofone or more automotive fuel materials that are stable andrepresentative of the samples of interest.9. Sampling9.1 A sample shall be taken in accordance

40、with the instruc-tions in Practice D4057 or D4177, where appropriate. Do notshake samples, thus avoiding entrained air. Analyze samplesimmediately after pouring into a sample cell and allowing theescape of the air bubbles caused by mixing.9.2 For the measurement of low sulfur contents disposablecell

41、s are recommended. Preparation of sample cells must bedone with care and by following any advice from the supplier.A freshly prepared sample cell including film is required priorto analyzing the samples. Avoid touching the inside of thesample cell or portion of the window film in the cell or in thei

42、nstrument window that is exposed to X rays. Oil fromfingerprints affects the reading when analyzing for low level ofsulfur. Ensure that the film is not scratched, especially by thetear-off bar as it is withdrawn from the container. Wrinkles inthe film will affect the intensity of sulfur X rays trans

43、mitted.Therefore, it is essential that the film be taut and clean toensure reliable results. Film may become electrostaticallycharged during handling so it is important that the cell windowdoes not attract any dust, fiber, and hair. The analyzer will needrecalibration if the type or thickness of the

44、 window film ischanged.9.3 If the instrument has a replaceable secondary/safetywindow, it must be changed for every sample to ensure there isno cross-contamination. When changing it, follow the precau-tions given in 9.2.9.4 Impurities that may affect the measurement of lowlevels of sulfur have been

45、found in polyester films. All filmsmay vary in thickness from roll to roll. Therefore, the calibra-tion shall be verified after starting each new roll of film.9.5 Where laboratories use more than one XRF spectrom-eter or analyze different types of sample, a variety of cellwindow materials may be use

46、d. Always ensure that the correctfilm is clearly distinguished.10. Preparation of Apparatus10.1 Set up the apparatus in accordance with the manufac-turers instructions. Whenever possible, the instrument shouldremain energized to maintain optimum stability.10.2 When changing the helium gas cylinder o

47、r after asystem has been idle for a day or more ensure that the heliumpipes are purged of air by performing a dummy measurement.11. Calibration and Standardization11.1 Preparation of Calibration Standards:11.1.1 Preparation of Stock Calibration StandardAccurately weigh the nominal quantity of white

48、mineral oil tothe nearest 0.1 mg, as shown in Table 1, into a suitablenarrow-necked container, then accurately weigh in the nominalquantity of di-n-butyl sulfide. Mix thoroughly (a PTFE-coatedmagnetic stirrer is advisable) at room temperature. Calculatethe concentration of sulfur in the stock standa

49、rd to 1 mg kgusing the following equation:SStock5 DBS 3SDBS/DBS1MO!# 310000 (1)where:SStock= mg/kg of sulfur in the stock standard,DBS = actual mass of DBS, g,SDBS= the mass % of sulfur in DBS, typically 21.91 %, andMO = actual mass of white mineral oil, g.11.1.2 Preparation of Calibration StandardsAccuratelyweigh the nominal quantity of white mineral oil to the nearest0.1 mg, as shown in Table 2, into a suitable narrow-neckedcontainer, then accurately weigh in the nominal quantity ofstock standard. Mix thoroughly (a PTFE-coated magneticstirrer is advisable)