1、Designation: D7751 16Standard 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 yea
2、r 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. Scope*1.1 This test method covers the quantitative determinationof additive elements in unused lubricating oils and additi
3、vepackages, as shown in Table 1.1.2 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 listed in Table 1.1.3 Some lubric
4、ation 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 bring theconcentrations for all ele
5、ments 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 ahigh resolution semiconductor
6、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 in thisstandard.1.6.1 The pref
7、erred 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 determine the applica-bility of regula
8、tory 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 Assuranceand Control Charting Techniqu
9、es 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 Practice for Optimization, Sam
10、ple 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 Determination and application of prec
11、ision 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.3.2 Abbreviations:3.2.1 EDXRFEnergy Dispersive X-ray FluorescenceSpectrometry.3.2.2 FPFundamental Parameters.4. Summa
12、ry of Test Method4.1 A specimen is placed in the X-ray beam, and theappropriate regions of its spectrum are measured to give the1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03
13、on Elemental Analysis.Current edition approved Dec. 15, 2016. Published February 2017. Originallyapproved in 2011. Last previous edition approved in 2014 as D7751 141.DOI:10.1520/D7751-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service
14、astm.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-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.*A Summary of Changes
15、 section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decisi
16、on on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1fluorescent intensities of magnesium, phosphorus, sulfur,chlorine, calcium, zinc, and molybdenum. Other regions of thespectru
17、m are measured to compensate for matrix variation. Tooptimize the sensitivity for each element or group of elements,a combination of optimized excitation and detection conditions(for example, different primary beam filters (7.1.3), secondaryor polarization targets (7.1.4), and so forth) may be used.
18、 Themeasuring time should be kept as short as possible, typicallyunder 10 min per specimen.Avoid using different measurementconditions that yield only marginally better results for aspecific analyte. There may be a correction of measuredintensities for spectral overlap.4.1.1 Concentrations of the el
19、ements of interest are deter-mined by comparison of these intensities against a calibrationcurve using a fundamental parameters (FP) approach, possiblycombined with corrections from backscatter. The FP approachuses the physical processes forming the basis of X-ray fluo-rescence emission in order to
20、provide a theoretical model forthe correction of matrix effects. The correction term is calcu-lated from first principle expressions derived from basicphysical principles and contain physical constants and param-eters that include absorption coefficients, fluorescence yield,primary spectral distribu
21、tion and spectrometry geometry. Thecalculation of concentrations in samples is based on makingsuccessively better estimates of composition by an iterationprocedure.NOTE 1The algorithm used for the procedure is usually implementedin the instrument manufacturers software.4.2 The EDXRF spectrometer is
22、initially calibrated using aset of standards to collect the necessary intensity data. Eachcalibration line and any correction coefficient are obtained by aregression of this data, using the program supplied with thespectrometer. (WarningExposure to excessive quantities ofX-radiation is injurious to
23、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 that might be present. The X-ray spectrometer shouldbe operated in accordance with the regulations governing theuse of ionizing radia
24、tion.)5. Significance and Use5.1 Lubricating oils are formulated with organo-metallicadditives, which act, for example, as detergents, antioxidants,antifoaming, or antiwear agents, or a combination thereof.Some of these additives contain one or more of the followingelements: magnesium, phosphorus, s
25、ulfur, chlorine, calcium,zinc, and molybdenum. This test method provides a means ofdetermining the concentrations of these elements, which in turnprovides an indication of the additive content of these oils.5.2 Several additive elements and their compounds areadded to the lubricating oils to give be
26、neficial 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 for themonitoring of additive elements in lubricating oils.5.5 If this test method is applied to lubricating oils withmatrices signifi
27、cantly different from the calibration materialsspecified in this test method, the cautions and recommenda-tions in Section 6 should be observed when interpreting theresults.6. Interferences6.1 The additive elements found in lubricating oils willaffect the measured intensities from the elements of in
28、terest 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 the sample matrix. Also theX-radiation emitted from one element can further excite(enhance) another element. These inter-element effe
29、cts aresignificant at concentrations varying from 0.03 mass %, due tothe higher atomic number elements (for example,molybdenum), to 1 mass %, for the lower atomic numberTABLE 1 Elements and Range of ApplicabilityElement PLOQ in mass % Max Concentration inmass %Magnesium 0.018 0.10Phosphorous 0.024 0
30、.125Sulfur 0.008 1.94Chlorine 0.0007 0.05Calcium 0.002 0.44Zinc 0.040 0.143Molybdenum 0.004 0.047TABLE 2 Lubricants and Additive MaterialsElement Compounds Purpose/ApplicationCalcium Sulfonates, phenates Detergent inhibitors, dispersantsChlorine Trace contaminants, cleaning agentsMagnesium Sulfonate
31、s, phenates Detergent inhibitorsMolybdenum Dialkylithiophosphate dialkyldithiocarbamate, othermolybdenum complexesFriction modifier additivesPhosphorus Dithiophosphates, phosphates phosphites Anti-rusting agents, extreme pressure additives, anti-wearSulfur Base oils, sulfonates, thiophosphates, poly
32、sulfides 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, turbi
33、ne oils, automatictransmission fluids, railroad diesel engine oils, brake lubricantsD7751 162elements (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 e
34、nhancement.6.2 Absorption and enhancements effects will be correctedby corrections from the 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
35、Dispersive X-ray Fluorescent SpectrometerAny energy dispersive X-ray fluorescence spectrometer 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. Th
36、e voltage of the X-ray tube shall beprogrammable between 4 kV and at least 30 kV for preferentialexcitation 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 (Opt
37、ional)To make the exci-tation more selective and to reduce the intensity of backgroundradiation.7.1.4 Secondary or Polarization Targets, or Both(Optional)To make the excitation more selective and toimprove peak-to-background ratio.7.1.5 Signal Conditioning and Data Handling ElectronicsThat include t
38、he functions of X-ray intensity counting, spectrahandling by background variation correction, overlapcorrections, inter-elements effects corrections, and conversionof X-ray intensity into concentration.7.1.6 Helium Purgeable Optical Path (Optional)Heliumpurge improves the sensitivity of low energy X
39、-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 film.7.1.8 Sample FilmSuitable films include polypropylene,polyester, and polycarbonate with thickness from 3.5 m to8 m. A thick film may limit the
40、performance for low atomicnumbers (for example, Magnesium).7.2 Instrument Setting-Up Samples (Elemental ReferenceSamples) (Optional)To quantify spectral overlaps. These arenot required when the instruments software does includesoftware to deconvolute spectra.7.3 Drift Correction Monitors (Optional)T
41、o correct forinstrumental drift.At least two samples are necessary to correctboth sensitivity and possible changes in the background. Foreach element and scatter region, there shall be one providing acount rate similar to samples from the upper end of thecalibration and another providing a count rat
42、e 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 been found to be satisfactory. Elementalreference samples (7.2) may also be used.7.3.1 Drift correction is usually implemented automaticallyin softwa
43、re, although the calculation can readily be donemanually. For X-ray instruments that are highly stable, themagnitude of the drift correction factor may not differ signifi-cantly from unity.7.4 Quality Control (QC) SamplesSamples for use inestablishing and monitoring the stability and precision of an
44、analytical measurement system. Use homogeneous materials,similar to samples of interest and available in sufficientquantity to be analyzed regularly for a long period of time.7.5 For additional information, also refer to Practice D7343.8. Reagents and Materials8.1 Purity of Reagents4Reagent grade ch
45、emicals shall beused in all tests. 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
46、the reagent is of sufficientlyhigh 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). I
47、f diluted samples are analyzed at low levels of sulfur, alower sulfur content of the diluent solvent should be used andmust be corrected for when recalculating the concentrations forthe original, not-diluted sample. The precision stated in this testmethod does not apply to diluted samples.8.3 Helium
48、 GasMinimum purity 99.9 %.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.
49、4.2.2 Zinc Cyclohexanebutyrate, 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 mass % chlo-rine).8.4.2.7 Commercially available single element standard formolybdenum based on molybdenumsulfonate.8.4.2.8 Stabilizers, 2-ethylhexanoic acid, 2-ethylamine, alsoproprietary stabilizer/chelating solutions are available co
