1、Designation: D7751 111D7751 12Standard 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 NOTEAdded research report footnote editorially in November 2011.1. Scope1.1 This test method covers the quantitati
3、ve determination of additive elements in unused lubricating 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% for magnesium, 0.003 % for phosphorus, 0.002 % for sulfur, 0.00
4、1 % for chlorine, 0.003 % for calcium, 0.001% for zinc, and 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 eleme
5、nts into 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 theexpecte
6、d concentrations 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 ad
7、jacent 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
8、of measurement 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 and Lubricants and is the direct responsibility of Subcommittee D02.03 onElemental Analysis.Current editio
9、n approved Oct. 1, 2011Dec. 1, 2012. Published November 2011March 2013. DOI:10.1520/D7751-11E01.Originally approved in 2011. Last previous editionapproved in 2011 as D7751 11E01. DOI:10.1520/D7751-12.TABLE 1 Elements and Range of ApplicabilityElement Concentration Range in mass %Magnesium 0.02 to 0.
10、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 previous version. Bec
11、auseit 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.Copyright ASTM International, 100
12、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 the user of this standard to establish appropriate safety and health practices and det
13、ermine 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 of Petroleum and Petroleum ProductsD6299 Practice for Applying Statistical Quality Ass
14、urance 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 LubricantsD6792 Practice for Quality System in Petroleum Products and Lubricants Testing Laborat
15、oriesD7343 Practice for Optimization, Sample Handling, Calibration, and Validation of X-ray Fluorescence Spectrometry Methodsfor Elemental Analysis of Petroleum Products and LubricantsE1621 Guide for X-Ray Emission Spectrometric Analysis2.2 ISO Standards:3ISO 4259 Determination and application of pr
16、ecision 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 radiation.3.2 Abbreviations:3.2.1 EDXRFEnergy Dispersive X-ray Fluorescence Spectrometry.3.2.2 FPFundamental Parameters.4. Su
17、mmary 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, phosphorus, sulfur, chlorine, calcium, zinc, and molybdenum. Other regions of the spectrum aremeasured to compensate for matrix va
18、riation. 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 conditions should be used in order to keep theanalysis time as short as possible, typically under ten minutes). There may be a corre
19、ction of measured intensities for spectraloverlap.4.1.1 Concentrations of the elements of interest are determined by comparison of these intensities against a calibration curveusing a fundamental parameters (FP) approach, possibly combined with corrections from backscatter. The FP approach uses thep
20、hysical 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 calculated from first principle expressions derived from basic physical principles and containphysical constants and parameters that
21、include absorption coefficients, fluorescence yield, primary spectral distribution andspectrometry geometry. The calculation of concentrations in samples is based on making successively better estimates ofcomposition by an iteration procedure.NOTE 1The algorithm used for the procedure is usually imp
22、lemented in the instrument manufacturers software.4.2 The EDXRF spectrometer is initially calibrated using a set of standards to collect the necessary intensity data. Eachcalibration line and any correction coefficient are obtained by a regression of this data, using the program supplied with thespe
23、ctrometer. (WarningExposure to excessive quantities of X-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 scattered radiationthat might be present. The X-ray spectrometer sho
24、uld be operated in accordance with the regulations governing the use of ionizingradiation.)5. Significance and Use5.1 Lubricating oils are formulated with organo-metallic additives, which act, for example, as detergents, antioxidants,antifoaming, or antiwear agents, or a combination thereof. Some of
25、 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 determining theconcentrations of these elements, which in turn provides an indication of the additive content of these oils.5.2
26、Additive packages are the concentrates that are used to blend lubricating oils.2 For referencedASTM standards, visit theASTM website, 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
27、 the ASTM website.3 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.D7751 1225.3 This test method is primarily intended to be used for the monitoring of additive elements in lubricating oils.5.4 I
28、f this test method is applied to lubricating oils 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 lubri
29、cating oils will affect the measured intensities from 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 elem
30、ent can further excite (enhance) another element.These 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 presen
31、tat significant concentrations and an inter-element 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 Th
32、ere can be spectral overlap of one element onto another, 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
33、 following features:7.1.1 Source of X-ray ExcitationX-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.
34、2 X-ray DetectorSemiconductor detector with high sensitivity 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 (
35、Optional)To make the excitation more selective and 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 correct
36、ions, and conversion of X-rayintensity into concentration.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 tr
37、ansparent film.7.1.8 Sample FilmSuitable films include 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
38、 spectral overlaps. These are notrequired when the instruments software does include software to deconvolute spectra.7.3 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 ea
39、ch element and scatter region, there shall be one providing 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 p
40、ellet have all been found tobe satisfactory. Elemental 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 corr
41、ection factor may not differ significantly from unity.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 quanti
42、ty tobe analyzed regularly for a long period of time.7.5 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.D7751 1238. Reagents and Materials8.1 Purity of Reagents4Reagent grade chemi
43、cals shall be used in all tests. Unless otherwise indicated, it 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
44、the reagent is of sufficiently high purityto permit its use without 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)
45、.8.3 Helium GasMinimum purity 99.9 %.8.4 Calibration Standard Materials: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 %
46、 calcium.8.4.2.2 Zinc Cyclohexanebutyrate, approximately 16.2 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 (approximately 21.9 mass % sulfur).8.4.2.5 Magnesium-2-ethylhexoate, (2.99 % magnesium).8.
47、4.2.6 1-Chlorooctane, 98 % purity, (23.9 mass % chlorine).8.4.2.7 Commercially available single element standard for molybdenum based on molybdenumsulfonate.8.4.2.8 Stabilizers, 2-ethylhexanoic acid, 2-ethylamine, also proprietary stabilizer/chelating solutions are available commer-cially. Stabilize
48、rs shall be free of the additive element.NOTE 3In addition to the calibration standard materials identified in 8.4, single or multielement calibration standards can also be prepared frommaterials similar to the samples being analyzed, provided the calibration standards to be used have previously bee
49、n characterized by independent primary(for example, gravimetric or volumetric) analytical techniques to establish the elemental concentration mass % levels.9. Hazards9.1 Occupational health and safety standards for X-rays and ionizing radiation shall be observed. It is also recommended thatproper practices be followed as presented by most manufactures documentation or described in Guide E1621.10. Sampling and Test Specs and Units10.1 Samples shall be taken in accordance with the instructions in Practices D4057 or D4177. For sample handling, also refe
