1、Designation: D7751 141Standard Test Method forDetermination of Additive Elements in Lubricating Oils byEDXRF Analysis1This standard is issued under the fixed designation D7751; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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.1NOTETable 4 was corrected editorially in November 2015.1. Scope*1.1 This test method covers the quantitative determinationo
3、f additive elements in unused lubricating oils and additivepackages, as shown in Table 1. The pooled limit of quantitationof this test method as obtained by statistical analysis ofinterlaboratory test results is 0.02 % for magnesium, 0.003 %for phosphorus, 0.002 % for sulfur, 0.001 % for chlorine,0.
4、003 % for calcium, 0.001 % for zinc, and 0.002 % formolybdenum.1.2 Additive packages require dilution with a contaminationfree diluent (base oil) prior to analysis. The dilution factor hasto be calculated from the expected concentrations to bring theconcentrations for all elements into the ranges li
5、sted in Table 1.1.3 Some lubrication oils will contain higher concentrationsthan the maximum concentrations listed in Table 1. Thesesamples require dilution with a contamination free diluent(base oil) prior to analysis. The dilution factor has to becalculated from the expected concentrations to brin
6、g theconcentrations for all elements into the ranges listed in Table 1.1.4 This test method is limited to the use of energydispersive X-ray fluorescence (EDXRF) spectrometers em-ploying an X-ray tube for excitation in conjunction with theability to separate the signals of adjacent elements by using
7、ahigh resolution semiconductor detector.1.5 This test method uses inter-element correction factorscalculated from a fundamental parameters (FP) approach orfrom another matrix correction method.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included
8、 in thisstandard.1.6.1 The preferred concentration units are mg/kg or mass%.1.7 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 determi
9、ne the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuran
10、ceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum Products andLubricantsD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing LaboratoriesD7343
11、 Practice for Optimization, Sample Handling,Calibration, and Validation of X-ray Fluorescence Spec-trometry Methods for Elemental Analysis of PetroleumProducts and LubricantsE1621 Guide for Elemental Analysis by Wavelength Disper-sive X-Ray Fluorescence Spectrometry2.2 ISO Standards:3ISO 4259 Determ
12、ination and application of precision data inrelation to methods of test3. Terminology3.1 Definitions:3.1.1 energy dispersive X-ray spectrometry, nXRF spec-trometry applying energy dispersive selection of radiation.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products
13、, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Dec. 1, 2014. Published January 2015. Originallyapproved in 2011. Last previous edition approved in 2012 as D7751 12.DOI:10.1520/D7751-14E01.2For referenced ASTM stand
14、ards, 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 International Organization for Standardization (ISO), 1, ch. dela Voie-
15、Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Abbreviations:3.2.1 EDXRFEnergy Dispersive X-ray Flu
16、orescenceSpectrometry.3.2.2 FPFundamental Parameters.4. Summary of Test Method4.1 A specimen is placed in the X-ray beam, and theappropriate regions of its spectrum are measured to give thefluorescent intensities of magnesium, phosphorus, sulfur,chlorine, calcium, zinc, and molybdenum. Other regions
17、 of thespectrum are measured to compensate for matrix variation. Tooptimize the sensitivity for each element or group of elements,a combination of optimized excitation and detection conditionsmay be used (no more than two conditions should be used inorder to keep the analysis time as short as possib
18、le, typicallyunder ten minutes). There may be a correction of measuredintensities for spectral overlap.4.1.1 Concentrations of the elements of interest are deter-mined by comparison of these intensities against a calibrationcurve using a fundamental parameters (FP) approach, possiblycombined with co
19、rrections from backscatter. The FP approachuses the physical processes forming the basis of X-ray fluo-rescence emission in order to provide a theoretical model forthe correction of matrix effects. The correction term is calcu-lated from first principle expressions derived from basicphysical princip
20、les and contain physical constants and param-eters that include absorption coefficients, fluorescence yield,primary spectral distribution and spectrometry geometry. Thecalculation of concentrations in samples is based on makingsuccessively better estimates of composition by an iterationprocedure.NOT
21、E 1The algorithm used for the procedure is usually implementedin the instrument manufacturers software.4.2 The EDXRF spectrometer is initially calibrated using aset of standards to collect the necessary intensity data. Eachcalibration line and any correction coefficient are obtained by aregression o
22、f this data, using the program supplied with thespectrometer. (WarningExposure to excessive quantities ofX-radiation is injurious to health. The operator needs to takeappropriate actions to avoid exposing any part of their body,not only to primary X-rays, but also to secondary or scatteredradiation
23、that might be present. The X-ray spectrometer shouldbe operated in accordance with the regulations governing theuse of ionizing radiation.)5. Significance and Use5.1 Lubricating oils are formulated with organo-metallicadditives, which act, for example, as detergents, antioxidants,antifoaming, or ant
24、iwear agents, or a combination thereof.Some of these additives contain one or more of the followingelements: magnesium, phosphorus, sulfur, chlorine, calcium,zinc, and molybdenum. This test method provides a means ofdetermining the concentrations of these elements, which in turnprovides an indicatio
25、n of the additive content of these oils.5.2 Several additive elements and their compounds areadded to the lubricating oils to give beneficial performance(Table 2).5.3 Additive packages are the concentrates that are used toblend lubricating oils.5.4 This test method is primarily intended to be used f
26、or themonitoring of additive elements in lubricating oils.5.5 If this test method is applied to lubricating oils withmatrices significantly different from the calibration materialsspecified in this test method, the cautions and recommenda-tions in Section 6 should be observed when interpreting there
27、sults.6. Interferences6.1 The additive elements found in lubricating oils willaffect the measured intensities from the elements of interest toa varying degree. In general the X-radiation emitted by theelement of interest can be absorbed by itself (self-absorption)or by the other elements present in
28、the sample matrix. Also theX-radiation emitted from one element can further excite(enhance) another element. These inter-element effects aresignificant at concentrations varying from 0.03 mass %, due tothe higher atomic number elements (for example,molybdenum), to 1 mass %, for the lower atomic numb
29、erelements (for example, sulfur). If an element is present atsignificant concentrations and an inter-element correction forthat element is not employed, the results can be low due toabsorption or high due to enhancement.6.2 Absorption and enhancements effects will be correctedby corrections from the
30、 FP approach or by other matrixcorrection models.6.3 There can be spectral overlap of one element ontoanother, and the instrument must include correction proceduresfor any such overlaps.7. Apparatus7.1 Energy Dispersive X-ray Fluorescent SpectrometerAny energy dispersive X-ray fluorescence spectrome
31、ter can beused if its design incorporates at least the following features:7.1.1 Source of X-ray ExcitationX-ray tube withpalladium, silver, rhodium, or tungsten target. Other targetsmay be suitable as well. The voltage of the X-ray tube shall beprogrammable between 4 kV and at least 30 kV for prefer
32、entialexcitation of elements or groups of elements.7.1.2 X-ray DetectorSemiconductor detector with highsensitivity and a spectral resolution value not to exceed 175 eVat 5.9 keV.7.1.3 Primary Beam Filters (Optional)To make the exci-tation more selective and to reduce the intensity of backgroundradia
33、tion.TABLE 1 Elements and Range of ApplicabilityElement Concentration Range in mass %Magnesium 0.02 to 0.4Phosphorous 0.003 to 0.25Sulfur 0.002 to 1.5Chlorine 0.001 to 0.4Calcium 0.003 to 1.0Zinc 0.001 to 0.25Molybdenum 0.002 to 0.05D7751 14127.1.4 Secondary or Polarization Targets, or Both(Optional
34、)To make the excitation more selective and toimprove peak-to-background ratio.7.1.5 Signal Conditioning and Data Handling ElectronicsThat include the functions of X-ray intensity counting, spectrahandling by background variation correction, overlapcorrections, inter-elements effects corrections, and
35、 conversionof X-ray intensity into concentration.7.1.6 Helium Purgeable Optical Path (Optional)Heliumpurge improves the sensitivity of low energy X-rays emittedfrom low atomic number elements (Z 22).7.1.7 Sample CellsProviding a depth of at least 6 mm andequipped with replaceable X-ray transparent f
36、ilm.7.1.8 Sample FilmSuitable films include polypropylene,polyester, and polycarbonate with thickness from 3.5 m to 8m. A thick film may limit the performance for low atomicnumbers (for example, Magnesium).7.2 Instrument Setting-Up Samples (Elemental ReferenceSamples) (Optional)To quantify spectral
37、overlaps. These arenot required when the instruments software does includesoftware to deconvolute spectra.7.3 Drift Correction Monitors (Optional)To correct forinstrumental drift.At least two samples are necessary to correctboth sensitivity and possible changes in the background. Foreach element and
38、 scatter region, there shall be one providing acount rate similar to samples from the upper end of thecalibration and another providing a count rate as if from ablank. This last can be a blank oil. For the high concentrationof each element, a glass disk, XRF fusion bead, or pressedpellet have all be
39、en found to be satisfactory. Elementalreference samples (7.2) may also be used.7.3.1 Drift correction is usually implemented automaticallyin software, although the calculation can readily be donemanually. For X-ray instruments that are highly stable, themagnitude of the drift correction factor may n
40、ot differ signifi-cantly from unity.7.4 Quality Control (QC) Samples (Optional)Samples foruse in establishing and monitoring the stability and precision ofan analytical measurement system. Use homogeneousmaterials, similar to samples of interest and available insufficient quantity to be analyzed reg
41、ularly for a long period oftime.7.5 For additional information, also refer to Practice D7343.NOTE 2Verification of system control through the use of QC samplesand control charting is highly recommended.8. Reagents and Materials8.1 Purity of Reagents4Reagent grade chemicals shall beused in all tests.
42、 Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available. Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh
43、 purity to permit its use without lessening the accuracy ofthe determination.8.2 Diluent SolventA suitable solvent containing less than10 mg/kg of sulfur and containing less than 1 mg/kg of metalsas well as of all other elements of interest (for example, baseoil).8.3 Helium GasMinimum purity 99.9 %.
44、8.4 Calibration Standard Materials:8.4.1 Commercially available calibration solutions.8.4.2 Certified concentration solutions, of liquid organome-tallic salts, the following standard materials can be used:8.4.2.1 Calcium 2-Ethylhexanoate, approximately12.3 mass % calcium.8.4.2.2 Zinc Cyclohexanebuty
45、rate, approximately16.2 mass % zinc.8.4.2.3 Bis(2-Ethylhexyl)Hydrogen Phosphate, 97 % purity(approximately 9.62 mass % phosphorus).8.4.2.4 Di-n-butyl Sulfide, 97 % purity (approximately21.9 mass % sulfur).8.4.2.5 Magnesium-2-ethylhexoate, (2.99 % magnesium).8.4.2.6 1-Chlorooctane, 98 % purity, (23.9
46、 mass % chlo-rine).8.4.2.7 Commercially available single element standard formolybdenum based on molybdenumsulfonate.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical S
47、ociety, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.TABLE 2 Lubricants and Additive MaterialsElement Compounds Purpose/ApplicationCalcium Sulfonates, ph
48、enates Detergent inhibitors, dispersantsChlorine Trace contaminants, cleaning agentsMagnesium Sulfonates, phenates Detergent inhibitorsMolybdenum Dialkylithiophosphate dialkyldithiocarbamate, othermolybdenum complexesFriction modifier additivesPhosphorus Dithiophosphates, phosphates phosphites Anti-
49、rusting agents, extreme pressure additives, anti-wearSulfur Base oils, sulfonates, thiophosphates, polysulfides andother sulfurized componentsDetergents, extreme pressure additives, anti-wearZinc Dialkyldithiophosphates, dithiocarbamates, phenolatescarboxylatesAnti-oxidant, corrosion inhibitors, anti-wear additives, detergents, crankcaseoils, hypoid gear lubricants, aircraft piston engine oils, turbine oils, automatictransmission fluids, railroad diesel engine oils, brake lubricantsD7751 14138.4.2.8 Stabilizers, 2-ethylhexanoic acid, 2-ethylamine, al
