1、Designation: D6334 12Standard Test Method forSulfur in Gasoline by Wavelength Dispersive X-RayFluorescence1This standard is issued under the fixed designation D6334; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 quantitative determinationof total sulfur in gasoline and gasoline-oxygenate blends. ThePooled
3、 Limit of Quantitation (PLOQ) was determined to be 15mg/kg. Therefore, the practical range for this test method isfrom 15 to 940 mg/kg.NOTE 1This concentration range is based on that used in theinterlaboratory round robin, which shows that the range of sulfur in theround robin samples was from 1.5 t
4、o 940 mg/kg; however, below 15mg/kg, the reproducibility approaches 100 % of the concentration.1.2 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 pr
5、actices and determine the applica-bility of regulatory limitation prior to use.1.3 The values stated in SI units are to be regarded as thestandard. The preferred units are mg/kg sulfur.2. Referenced Documents2.1 ASTM Standards:2D2622 Test Method for Sulfur in Petroleum Products byWavelength Dispersi
6、ve X-ray Fluorescence SpectrometryD3210 Test Method for Comparing Colors of Films fromWater-Emulsion Floor PolishesD4045 Test Method for Sulfur in Petroleum Products byHydrogenolysis and Rateometric ColorimetryD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Au
7、tomatic Sampling of Petroleum andPetroleum ProductsD4294 Test Method for Sulfur in Petroleum and PetroleumProducts by Energy Dispersive X-ray Fluorescence Spec-trometryD5453 Test Method for Determination of Total Sulfur inLight Hydrocarbons, Spark Ignition Engine Fuel, DieselEngine Fuel, and Engine
8、Oil by Ultraviolet FluorescenceD5842 Practice for Sampling and Handling of Fuels forVolatility MeasurementD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate An
9、alyticalMeasurement System PerformanceD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing Laboratories3. Summary of Test Method3.1 The sample is placed in the X-ray beam, and theintensity of the sulfur K line at 5.373 is measured. Theintensity of a corrected background, mea
10、sured at a recom-mended wavelength of 5.190 , or if a rhodium tube is used,5.437 , is subtracted from this intensity. The resultant netcounting rate is then compared to a previously preparedcalibration curve or equation to obtain the concentration ofsulfur in mg/kg. (WarningExposure to excessive qua
11、ntitiesof X radiation is injurious to health. Therefore, it is imperativethat the operator avoid exposing any part of his or her person,not only to primary X-rays, but also to secondary or scatteredradiation that might be present. The X-ray spectrometer shouldbe operated in accordance with the regul
12、ations of recommen-dations governing the use of ionizing radiation.)4. Significance and Use4.1 Knowledge of the presence of sulfur in petroleumproducts, especially fuels, helps predict performancecharacteristics, potential corrosion problems, and vehicle emis-sion levels. In addition, some regulator
13、y agencies mandatereduced levels of sulfur in reformulated type gasolines.5. Interferences5.1 Fuels with compositions that vary from those specifiedin 9.1 may be analyzed with standards made from basematerials that are of similar composition to minimize matrixeffects.1This test method is under the j
14、urisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved Dec. 1, 2012. Published December 2012. Originallyapproved in 1962. Last previous edition approved in 2007 as D633407. DOI:10.152
15、0/D6334-12.2For 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.*A Summary of Changes section appears at the end o
16、f this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.1.1 Fuels containing oxygenates may be analyzed usingstandards prepared with similar amounts of the same oxygenateadded to the standard dilution matrix. However, round r
17、obinstudies done by the Western States PetroleumAssociation haveshown no significant bias in determining sulfur in gasolineswith and without oxygenates at regulatory levels (0 to 2.7weight percent oxygen).5.1.2 Methanol fuels (M85 and M100) exhibit interferencesat this level of detection (100 mg/kg)
18、. They can be analyzedusing a calibration curve produced by diluting the standards ina similar matrix of M85 or M100 or by Test Method D2622.6. Apparatus6.1 Wavelength Dispersive X-Ray Fluorescence Spectrom-eter (WDXRF), equipped for soft ray detection in the 5.37 range. For optimum sensitivity to s
19、ulfur, equip the instrumentwith the following:6.1.1 Optical Path, of helium.6.1.2 Pulse-Height Analyzer, or other means of energydiscrimination.6.1.3 Detector, designed for the detection of long wave-length X-rays.6.1.4 Analyzing Crystal, suitable for the dispersion of sulfurK X-rays within the angu
20、lar range of the spectrometeremployed. Pentaerythritol and germanium are the mostpopular, although materials, such as EDDT,ADP, graphite, andquartz, may be used.6.1.5 X-Ray Tube, capable of exciting sulfur Kradiation.Tubes with anodes of rhodium, chromium, and scandium aremost popular, although othe
21、r anodes may be suitable.7. Reagents7.1 Di-n-Butyl Sulfide (MW 146.30), a high-purity gradestandard with a certified sulfur analysis.7.2 Thiophene MW 84.14), a high-purity (98+ %) gradestandard with a certified sulfur analysis.7.3 2-Methylthiophene MW 98.17), a high purity (98+ %)grade standard with
22、 a standard sulfur analysis.7.4 2,2,4-Trimethylpentane, (isooctane), reagent grade,MW-114.23.7.5 Methylbenzene, (Toluene), reagent grade, MW-92.14.7.6 Drift Correction Monitor(s), (Optional), several differ-ent materials have been found to be suitable for use as driftcorrection monitors. Examples of
23、 sulfur containing materialsthat meet these requirements are renewable liquid petroleummaterials, semipermanent solids, pressed powder pellets, metalalloys, or fused glass disks. Bracket the calibration range withconcentrations of monitor samples. The counting rate for eachmonitor is determined duri
24、ng calibration (see 9.7) and again atthe time of analysis (see 10.1). These counting rates are used tocalculate a drift correction factor (see 11.1).7.7 Calibration Check Standards, one or more liquid petro-leum or product standards of known sulfur content (which donot represent one of the samples p
25、repared in Section 9) areused to verify the accuracy of the calibration curve.7.8 Quality Control (QC) Sample, one or more stable liquidpetroleum or product samples, which are used to verify that themeasurement system is in control. Preferably the QC sample(s)should be representative of the samples
26、typically analyzed. Incases where volatility of the QC sample(s) may affect thesample integrity, precautions need to be taken to minimize oreliminate sample losses prior to analysis to ensure that a stableand representative sample can be taken and analyzed over theperiod of intended use. It is permi
27、ssible to use calibrationstandards for this purpose. Since standard samples are dis-carded after each determination, it is recommended that alower cost material be used for daily calibration checks.8. Sampling and Specimen Preparation8.1 Samples shall be taken in accordance with the instruc-tions in
28、 Practice D4057, D4177, D5842,orD5854, whereappropriate.8.2 Clean and dry reusable cells before use. Disposablesample cups are not to be reused. Window material usually is8 m polyester, 8 m polycarbonate, or 6 m polypropylenefilm. Renewal of the window of the sample cup is essential forthe measureme
29、nt of each sample. Avoid touching the inside ofthe sample cup, the portion of the window film in the cup, orthe instrument window that is exposed to X-rays. Oil fromfingerprints can affect the reading when analyzing for lowlevels of sulfur. Wrinkles in the film will affect the number ofsulfur X-rays
30、 transmitted. Therefore, the importance of thefilms tautness and cleanliness cannot be over stressed. Reca-librate the analyzer when you change the type or thickness ofthe window film.8.3 Polyester films often contain impurities that may affectthe measurement of low levels of sulfur and may vary fro
31、m lotto lot. Therefore, if using a polyester film, check the calibrationwith the start of each new roll.8.4 X-ray films may vary in thickness from batch to batch.Check the calibration when starting a new roll of any film.8.5 Samples of high aromatic count may dissolve polyesterand polycarbonate film
32、s. In these cases, other materials besidesthese films may be used for X-ray windows, provided that theydo not contain any elemental impurities that can adverselyaffect the results obtained by this test method.9. Calibration9.1 Prepare calibration standards by the careful preparationby mass of a 50:5
33、0 mixture (based on sulfur content) of thecertified thiophene and 2-methylthiophene or n-butyl sulfidewith 20 to 80 % mixture of tolueneisooctane or other suitablebase material (see 5.1). Exact standards of the nominal sulfurconcentrations listed in Table 1 are recommended.9.2 Preparation of Stock S
34、tandard: Weigh approximately0.657 g of thiophene and 0.767 g of 2-methylthiophene andrecord the masses to the nearest 0.1 mg, or weigh 2.286 ofn-butyl sulfide to the nearest 0.1 mg. Add the standardmaterials to a tared 100 mL volumetric flask. Add mixedsolvent of 20 % toluene and 80 % isooctane (by
35、volume) orother base material (see 5.1) to a net mass of 50.000 + 0.010 g.This stock standard contains approximately 10 mg/g sulfur.D6334 122Correct the concentration by multiplying the measured massesby the sulfur equivalency in each of the standards, that isthiophene grams 0.3803 purity plus 2-met
36、hylthiophenegrams 0.3260 purity (or n-butyl sulfide grams 0.2191 purity) = weight of sulfur in the standard solution. Divide thisnumber by the total mass of the standards and base materialadded to them, multiply by 1000 mg/g and the result is theactual sulfur concentration in mg/g. This calculation
37、is asfollows:S, mg/g 5 1000 3T 30.3803 3P1M 30.3260 3PF(1)S, mg/g 5 1000 3DB 30.2187 3PF(2)where:S = final sulfur concentration,T = mass of thiophene added,M = mass of 2-methylthiophene added,DB = mass of di- n-butyl sulfide added,P = purity of the standard material, andF = final mass of mixture.9.3
38、 Preparation of Diluted Standard: Dilute 25.0 mL ofstock standard to 250 mL using the base material. This gives astandard of approximately 1000 mg/kg. Divide the standardconcentration calculated in 9.2 by 10 to determine the actualconcentration.9.4 Serial Dilutions: Prepare serial dilutions of the d
39、ilutedstandard by diluting the following volumes to 100 mL usingthe base material:0.5 mL = 5 mg/kg1.0 mL = 10 mg/kg5.0 mL = 50 mg/kg10.0 mL = 100 mg/kg25.0 mL = 250 mg/kg50.0 mL = 500 mg/kgDiluted Standard = 1000 mg/kgNOTE 2Prepare calibrations up to 1000 mg/kg sulfur, and dilutesamples with higher
40、concentrations of sulfur to within this concentrationrange.9.5 Establish calibration curve data by carefully measuringthe net intensity of the emitted sulfur radiation from each of thestandards by the procedure described in Sections 10 and 11.9.6 Construct a calibration model by:9.6.1 Using the soft
41、ware and algorithms supplied by theinstrument manufacturer.9.6.2 Fitting the data to an equation of the type:S 5 aR1b (3)where:S = sulfur concentration, mg/kg,R = net intensity for the sulfur radiation,a = slope of the calibration curve, andb = intercept of the calibration curve.9.6.3 Plot corrected
42、 net intensity in counts per second (cps)versus sulfur concentration. Plot data in two ranges listed inTable 1.9.7 During collection of calibration data, measure the inten-sity of the drift monitor standards. Use the intensities fromthese standards to correct for day to day instrument sensitivity.Th
43、is value corresponds to A in Eq 5, Section 11. Manyinstrument manufacturers have built drift correction proceduresinto their software.9.8 At the completion of the calibration, measure one ormore independent calibration check standards to verify theaccuracy of the calibration curve. These standards (
44、see 7.7) areindependent of the calibration set. The measured value shallagree with the standard value within 62 % relative or 2 ppm,whichever is greater.NOTE 3NIST traceable gasoline standards are available at the 1, 10,40, and 300 mg/kg levels. Other concentrations may be prepared bydilution of the
45、se standards with a solvent of similar matrix to the standardspreviously prepared.NOTE 4NIST has suggested a “designer” method for the preparationof NIST traceable fossil fuel standards with concentrations intermediate toSRM values for sulfur. Laboratories can mix and prepare standards fordistillate
46、 fuels oils, residual fuel oil in almost any desired concentrationswith uncertainties that are calculable and traceable to NIST-certifiedvalues. This method enables the SRM user to create a customized seriesof calibration and quality control test samples.3NOTE 5A DVD available from NIST includes the
47、 above cited paperplus subsequent papers dealing with this subject as well as programmablespreadsheet to calculate blend concentrations and uncertainties. Some ofthe subsequent papers discuss the actual procedure to use when mixingrather than the proof of concept given in the first paper.410. Proced
48、ure10.1 Measure the intensity of the drift correction monitor(s)used in 9.7. The value determined corresponds to B in Eq 5,Section 11. This measurement may not be required on highstability instrumentation. Determine the value of FinEq 6,Section 11 at regular intervals by measuring the peak andbackgr
49、ound count rates on the solvent blank. This measure-ment may not be needed on some instruments.10.2 Place the sample in an appropriate cell using tech-niques consistent with good practice for the particular instru-ment being used. Although sulfur radiation will penetrate onlya small distance into the sample, scatter from the sample cupand the sample may vary to such an extent that a specificamount or a minimum amount of sample shall be used.Generally, filling the cup to one-half capacity is sufficient.3Kelly. W.R., MacDonald, B. S., and Leigh, S. D
