1、Designation: D7751 12D7751 14Standard 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,
2、 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. Scope Scope*1.1 This test method covers the quantitative determination of additive elements in unused lubricating
3、oils and additive packages,as shown in Table 1. The pooled limit of quantitation of this test method as obtained by statistical analysis of interlaboratory testresults is 0.02%0.02 % for magnesium, 0.003 % 0.003 % for phosphorus, 0.002 % 0.002 % for sulfur, 0.001 % 0.001 % forchlorine, 0.003 % 0.003
4、 % for calcium, 0.001 % 0.001 % for zinc, and 0.002 % 0.002 % for molybdenum.1.2 Additive packages require dilution with a contamination free diluent (base oil) prior to analysis. The dilution factor has tobe calculated from the expected concentrations to bring the concentrations for all elements in
5、to the ranges listed in Table 1.1.3 Some lubrication oils will contain higher concentrations than the maximum concentrations listed in Table 1. These samplesrequire dilution with a contamination free diluent (base oil) prior to analysis. The dilution factor has to be calculated from theexpected conc
6、entrations to bring the concentrations for all elements into the ranges listed in Table 1.1.4 This test method is limited to the use of energy dispersive X-ray fluorescence (EDXRF) spectrometers employing an X-raytube for excitation in conjunction with the ability to separate the signals of adjacent
7、 elements by using a high resolutionsemiconductor detector.1.5 This test method uses inter-element correction factors calculated from a fundamental parameters (FP) approach or fromanother matrix correction method.1.6 The values stated in SI units are to be regarded as standard. No other units of mea
8、surement are included in this standard.1.6.1 The preferred concentration units are mg/kg or mass %.1 This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analy
9、sis.Current edition approved Dec. 1, 2012Dec. 1, 2014. Published March 2013January 2015. Originally approved in 2011. Last previous edition approved in 20112012 asD7751 11E01. DOI:10.1520/D7751-12.12. DOI:10.1520/D7751-14.TABLE 1 Elements and Range of ApplicabilityElement Concentration Range in mass
10、 %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 0.05This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the
11、 previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary o
12、f Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States11.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof
13、 the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4177 Practice for Automatic Sampling
14、 of Petroleum and Petroleum ProductsD6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-ment System PerformanceD6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricant
15、sD6792 Practice for Quality System in Petroleum Products and Lubricants Testing LaboratoriesD7343 Practice for Optimization, Sample Handling, Calibration, and Validation of X-ray Fluorescence Spectrometry Methodsfor Elemental Analysis of Petroleum Products and LubricantsE1621 Guide for Elemental Ana
16、lysis by Wavelength Dispersive X-Ray Fluorescence Spectrometry2.2 ISO Standards:3ISO 4259 Determination and application of precision data in relation to methods of test3. Terminology3.1 Definitions:3.1.1 energy dispersive X-ray spectrometry, nXRF spectrometry applying energy dispersive selection of
17、radiation.3.2 Abbreviations:3.2.1 EDXRFEnergy Dispersive X-ray Fluorescence Spectrometry.3.2.2 FPFundamental Parameters.4. Summary of Test Method4.1 A specimen is placed in the X-ray beam, and the appropriate regions of its spectrum are measured to give the fluorescentintensities of magnesium, phosp
18、horus, sulfur, chlorine, calcium, zinc, and molybdenum. Other regions of the spectrum aremeasured to compensate for matrix variation. To optimize the sensitivity for each element or group of elements, a combination ofoptimized excitation and detection conditions may be used (no more than two conditi
19、ons should be used in order to keep theanalysis time as short as possible, typically under ten minutes). There may be a correction of measured intensities for spectraloverlap.4.1.1 Concentrations of the elements of interest are determined by comparison of these intensities against a calibration curv
20、eusing a fundamental parameters (FP) approach, possibly combined with corrections from backscatter. The FP approach uses thephysical processes forming the basis of X-ray fluorescence emission in order to provide a theoretical model for the correction ofmatrix effects. The correction term is calculat
21、ed from first principle expressions derived from basic physical principles and containphysical constants and parameters that include absorption coefficients, fluorescence yield, primary spectral distribution andspectrometry geometry. The calculation of concentrations in samples is based on making su
22、ccessively better estimates ofcomposition by an iteration procedure.NOTE 1The algorithm used for the procedure is usually implemented in the instrument manufacturers software.4.2 The EDXRF spectrometer is initially calibrated using a set of standards to collect the necessary intensity data. Eachcali
23、bration line and any correction coefficient are obtained by a regression of this data, using the program supplied with thespectrometer. (WarningExposure to excessive quantities of X-radiation is injurious to health. The operator needs to takeappropriate actions to avoid exposing any part of their bo
24、dy, not only to primary X-rays, but also to secondary or scattered radiationthat might be present. The X-ray spectrometer should be operated in accordance with the regulations governing the use of ionizingradiation.)5. Significance and Use5.1 Lubricating oils are formulated with organo-metallic addi
25、tives, 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 following elements:magnesium, phosphorus, sulfur, chlorine, calcium, zinc, and molybdenum. This test method provides a means of det
26、ermining theconcentrations of these elements, which in turn provides an indication of the additive content of these oils.5.2 Several additive elements and their compounds are added to the lubricating oils to give beneficial performance (Table 2).2 For referencedASTM standards, visit theASTM website,
27、 www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Gen
28、eva 20, Switzerland, http:/www.iso.org.D7751 1425.3 Additive packages are the concentrates that are used to blend lubricating oils.5.4 This test method is primarily intended to be used for the monitoring of additive elements in lubricating oils.5.5 If this test method is applied to lubricating oils
29、with matrices significantly different from the calibration materials specifiedin this test method, the cautions and recommendations in Section 6 should be observed when interpreting the results.6. Interferences6.1 The additive elements found in lubricating oils will affect the measured intensities f
30、rom the elements of interest to a varyingdegree. In general the X-radiation emitted by the element of interest can be absorbed by itself (self-absorption) or by the otherelements present in the sample matrix.Also the X-radiation emitted from one element can further excite (enhance) another element.T
31、hese inter-element effects are significant at concentrations varying from 0.03 mass %, due to the higher atomic number elements(for example, molybdenum), to 1 mass %, for the lower atomic number elements (for example, sulfur). If an element is presentat significant concentrations and an inter-elemen
32、t correction for that element is not employed, the results can be low due toabsorption or high due to enhancement.6.2 Absorption and enhancements effects will be corrected by corrections from the FP approach or by other matrix correctionmodels.6.3 There can be spectral overlap of one element onto an
33、other, and the instrument must include correction procedures for anysuch overlaps.7. Apparatus7.1 Energy Dispersive X-ray Fluorescent SpectrometerAny energy dispersive X-ray fluorescence spectrometer can be used ifits design incorporates at least the following features:7.1.1 Source of X-ray Excitati
34、onX-ray tube with palladium, silver, rhodium, or tungsten target. Other targets may be suitableas well. The voltage of the X-ray tube shall be programmable between 4 and at least 30 kV for preferential excitation of elementsor groups of elements.7.1.2 X-ray DetectorSemiconductor detector with high s
35、ensitivity and a spectral resolution value not to exceed 175 eV at 5.9keV.7.1.3 Primary Beam Filters (Optional)To make the excitation 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
36、 to improvepeak-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, overlap corrections, inter-elements effects corrections, and conversion of X-rayintensity into concen
37、tration.7.1.6 Helium Purgeable Optical Path (Optional)Helium purge improves the sensitivity of low energy X-rays emitted fromlow atomic number elements (Z 22).7.1.7 Sample CellsProviding a depth of at least 6 mm and equipped with replaceable X-ray transparent film.7.1.8 Sample FilmSuitable films inc
38、lude polypropylene, polyester, and polycarbonate with thickness from 3.5 to 8 m.Athickfilm may limit the performance for low atomic numbers (for example, Magnesium).7.2 Instrument Setting-Up Samples (Elemental Reference Samples) (Optional)To quantify spectral overlaps. These are notrequired when the
39、 instruments software does include software to deconvolute spectra.TABLE 2 Lubricants and Additive MaterialsElement Compounds Purpose/ApplicationCalcium Sulfonates, phenates Detergent inhibitors, dispersantsChlorine Trace contaminants, cleaning agentsMagnesium Sulfonates, phenates Detergent inhibito
40、rsMolybdenum Dialkylithiophosphate dialkyldithiocarbamate, othermolybdenum complexesFriction modifier additivesPhosphorus Dithiophosphates, phosphates phosphites Anti-rusting agents, extreme pressure additives, anti-wearSulfur Base oils, sulfonates, thiophosphates, polysulfides andother sulfurized c
41、omponentsDetergents, 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
42、 fluids, railroad diesel engine oils, brake lubricantsD7751 1437.3 Drift Correction Monitors (Optional)To correct for instrumental drift. At least two samples are necessary to correct bothsensitivity and possible changes in the background. For each element and scatter region, there shall be one prov
43、iding a count ratesimilar to samples from the upper end of the calibration and another providing a count rate as if from a blank. This last can bea blank oil. For the high concentration of each element, a glass disk, XRF fusion bead, or pressed pellet have all been found tobe satisfactory. Elemental
44、 reference samples (7.2) may also be used.7.3.1 Drift correction is usually implemented automatically in software, although the calculation can readily be done manually.For X-ray instruments that are highly stable, the magnitude of the drift correction factor may not differ significantly from unity.
45、7.4 Quality Control (QC) Samples (Optional)Samples for use in establishing and monitoring the stability and precision of ananalytical measurement system. Use homogeneous materials, similar to samples of interest and available in sufficient quantity tobe analyzed regularly for a long period of time.7
46、.5 For additional information, also refer to Practice D7343.NOTE 2Verification of system control through the use of QC samples and control charting is highly recommended.8. Reagents and Materials8.1 Purity of Reagents4Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it
47、 is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where suchspecifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use wit
48、hout lessening the accuracy of the determination.8.2 Diluent SolventA suitable solvent containing less than 10 mg/kg of sulfur and containing less than 1 mg/kg of metals aswell as of all other elements of interest (for example, base oil).8.3 Helium GasMinimum purity 99.9 %.8.4 Calibration Standard M
49、aterials:8.4.1 Commercially available calibration solutions.8.4.2 Certified concentration solutions, of liquid organometallic salts, the following standard materials can be used:8.4.2.1 Calcium 2-Ethylhexanoate, approximately 12.3 mass % 12.3 mass % calcium.8.4.2.2 Zinc Cyclohexanebutyrate, approximately 16.2 mass % 16.2 mass % zinc.8.4.2.3 Bis(2-Ethylhexyl)Hydrogen Phosphate, 97 % 97 % purity (approximately 9.62 mass % phosphorus).8.4.2.4 Di-n-butyl Sulfide, 97 % purity (approximately 21.9 mass % 21.9 mass % sulfur).8.4.2.5 Magnesium-2-ethylhexoate, (2.
