1、Designation: D 4951 06An American National StandardStandard Test Method forDetermination of Additive Elements in Lubricating Oils byInductively Coupled Plasma Atomic Emission Spectrometry1This standard is issued under the fixed designation D 4951; the number immediately following the designation ind
2、icates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies
3、of the Department of Defense.1. Scope*1.1 This test method covers the quantitative determinationof barium, boron, calcium, copper, magnesium, molybdenum,phosphorus, sulfur, and zinc in unused lubricating oils andadditive packages.1.2 The precision statements are valid for dilutions in whichthe mass
4、% sample in solvent is held constant in the range of1 to 5 mass % oil.1.3 The precision tables define the concentration rangescovered in the interlaboratory study. However, both lower andhigher concentrations can be determined by this test method.The low concentration limits are dependent on the sen
5、sitivityof the ICP instrument and the dilution factor. The highconcentration limits are determined by the product of themaximum concentration defined by the linear calibration curveand the sample dilution factor.1.4 Sulfur can be determined if the instrument can operate ata wavelength of 180 nm.1.5
6、The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 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-p
7、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1552 Test Method for Sulfur in Petroleum Products(High-Temperature Method)D 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 430
8、7 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 4628 Test Method for Analysis of Barium, Calcium,Magnesium, and Zinc in Unused Lubricating Oils byAtomic Absorption SpectrometryD 4927 Test Methods for Elemental Analysis of Lubricantand Additive ComponentsBarium, Calcium, P
9、hospho-rus, Sulfur, and Zinc by Wavelength-Dispersive X-RayFluorescence SpectroscopyD 5185 Test Method for Determination of Additive Ele-ments, Wear Metals, and Contaminants in Used Lubricat-ing Oils and Determination of Selected Elements in BaseOils by Inductively Coupled Plasma Atomic EmissionSpec
10、trometry (ICP-AES)D 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance3. Summary of Test Method3.1 A sample portion is weighed and diluted by mass withmixed xylenes or other solvent. An internal standard, which isrequired, is eithe
11、r weighed separately into the test solution or ispreviously combined with the dilution solvent. Calibrationstandards are prepared similarly. The solutions are introducedto the ICP instrument by free aspiration or an optionalperistaltic pump. By comparing emission intensities of ele-ments in the test
12、 specimen with emission intensities measuredwith the calibration standards and by applying the appropriateinternal standard correction, the concentrations of elements inthe sample are calculable.4. Significance and Use4.1 This test method usually requires several minutes persample. This test method
13、covers eight elements and thusprovides more elemental composition data than Test MethodD 4628 or Test Methods D 4927. In addition, this test methodprovides more accurate results than Test Method D 5185,which is intended for used lubricating oils and base oils.4.2 Additive packages are blends of indi
14、vidual additives,which can act as detergents, antioxidants, antiwear agents, andso forth. Many additives contain one or more elements coveredby this test method. Additive package specifications are based,1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubri
15、cants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in 1989. Last previous edition approved in 2002 as D 495102.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact
16、ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
17、shohocken, PA 19428-2959, United States.in part, on elemental composition. Lubricating oils are typi-cally blends of additive packages, and their specifications arealso determined, in part, by elemental composition. This testmethod can be used to determine if additive packages andunused lubricating
18、oils meet specifications with respect toelemental composition.5. Interferences5.1 SpectralThere are no known spectral interferencesbetween elements covered by this test method when using thespectral lines listed in Table 1. However, if spectral interfer-ences exist because of other interfering eleme
19、nts or selection ofother spectral lines, correct for the interference using thetechnique described in Test Method D 5185.5.2 Viscosity Index Improver EffectViscosity index im-provers, which can be present in multi-grade lubricating oils,can bias measurements. However, the biases can be reduced toneg
20、ligible proportion by using the specified solvent-to-sampledilution and an internal standard.6. Apparatus6.1 Inductively-Coupled Plasma Atomic EmissionSpectrometerEither a sequential or simultaneous spectrom-eter is suitable, if equipped with a quartz ICP torch and r-fgenerator to form and sustain t
21、he plasma.6.2 Analytical Balance, capable of weighing to 0.001 g or0.0001 g, capacity of 150 g.6.3 Peristaltic Pump, (Recommended)A peristaltic pumpis strongly recommended to provide a constant flow of solu-tion. The pumping speed must be in the range 0.5 to 3 mL/min.The pump tubing must be able to
22、withstand at least 6 hexposure to the dilution solvent. Fluoroelastomer copolymer3tubing is recommended.6.4 Solvent Dispenser, (Optional)A solvent dispensercalibrated to deliver the required weight of diluent can beadvantageous. Ensure that solvent drip does not affect accu-racy.6.5 Specimen Solutio
23、n Containers, of appropriate size, glassor polyolefin vials or bottles, with screw caps.6.6 Vortexer, (Optional)Vortex the sample plus diluentmixture until the sample is completely dissolved.6.7 Ultrasonic Homogenizer, OptionalA bath-type orprobe-type ultrasonic homogenizer can be used to homogenize
24、rthe test specimen.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals 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 specificati
25、ons are available.47.2 Base Oil, U.S.P. white oil, or a lubricating base oil thatis free of analytes, having a viscosity at room temperature asclose as possible to that of the samples to be analyzed.(WarningLubricating base oils can contain sulfur. Forpreparation of sulfur standards and blending of
26、additive pack-ages, white oil is recommended.)7.3 Internal Standard, (Required)An oil-soluble internalstandard element is required. The following internal standardswere successfully used in the interlaboratory study on preci-sion: Ag, Be, Cd, Co (most common), La, Mn, Pb, Y.7.4 Organometallic Standa
27、rdsMulti-element standards,containing known concentrations (approximately 0.1 mass %)of each element, can be prepared from the individual metalconcentrates. Refer to Practice D 4307 for a procedure forpreparation of multicomponent liquid blends. When preparingmulti-element standards, be certain that
28、 proper mixing isachieved. Commercially available multi-element blends (withknown concentrations of each element at approximately 0.1mass %) are also satisfactory.7.4.1 More than one multi-element standard can be neces-sary to cover all elements, and the user of this test method canselect the combin
29、ation of elements and their concentrations inthe multi-element standards. It can be advantageous to selectconcentrations that are typical of unused oils. However, it isimperative that concentrations are selected such that theemission intensities measured with the working standards canbe measured pre
30、cisely (that is, the emission intensities aresignificantly greater than background) and that these standards3Fluoroelastomer copolymer is manufactured as Viton, a trademark owned by E.I. duPont de Nemours.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washing
31、ton, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar 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 1 Elem
32、ents Determined and Suggested WavelengthsAElement Wavelength, nmBarium 233.53, 455.40, 493.41BoronB182.59, 249.68Calcium 315.88, 317.93, 364.4, 422.67Copper 324.75Magnesium 279.08, 279.55, 285.21Molybdenum 202.03, 281.62PhosphorusB177.51, 178.29, 213.62, 214.91, 253.40SulfurB180.73, 182.04, 182.62Zi
33、nc 202.55, 206.20, 213.86, 334.58, 481.05AThese wavelengths are only suggested and do not represent all possible choices.BWavelengths for boron, phosphorus, and sulfur below 190 nm require that a vacuum or inert gas purged optical path be used.D4951062represent the linear region of the calibration c
34、urve. Frequently,the instrument manufacturer publishes guidelines for determin-ing linear range.7.4.2 Some commercially available organometallic stan-dards are prepared from metal sulfonates and therefore containsulfur. For sulfur determinations, a separate sulfur standard canbe required. A sulfur s
35、tandard can be prepared by blendingNIST SRM 1622 with white oil.7.4.3 Metal sulfonates can be used as a sulfur standard if thesulfur content is known or determined by an appropriate testmethod such as Test Method D 1552.7.4.4 Petroleum additives can also be used as organometal-lic standards if their
36、 use does not adversely affect precision norintroduce significant bias.7.5 Dilution SolventMixed xylenes, o-xylene, and kero-sine were successfully used in the interlaboratory study onprecision.8. Internal Standardization (Required)8.1 The internal standard procedure requires that every testsolution
37、 (sample and standard) have the same concentration (ora known concentration) of an internal standard element that isnot present in the original sample. The internal standard isusually combined with the dilution solvent. Internal standardcompensation is typically handled in one of two different ways,
38、which can be summarized as follows.8.1.1 Calibration curves are based on the measured intensityof each analyte divided (that is, scaled) by the measuredintensity of the internal standard per unit internal standardelement concentration. Concentrations for each analyte in thetest specimen solution are
39、 read directly from these calibrationcurves.8.1.2 For each analyte and the internal standard element,calibration curves are based on measured (unscaled) intensi-ties. Uncorrected concentrations for each analyte in the testspecimen solution are read from these calibration curves.Corrected analyte con
40、centrations are calculated by multiplyingthe uncorrected concentrations by a factor equal to the actualinternal standard concentration divided by the uncorrectedinternal standard concentration determined by analysis.8.2 Dissolve the organometallic compound representing theinternal standard in diluti
41、on solvent and transfer to a dispensingvessel. The stability of this solution must be monitored andprepared fresh (typically weekly) when the concentration of theinternal standard element changes significantly. The concen-tration of internal standard element shall be at least 100 timesits detection
42、limit. A concentration in the range of 10 to 20mg/kg is typical.NOTE 1This test method specifies that the internal standard iscombined with the dilution solvent because this technique is common andefficient when preparing many samples. However, the internal standardcan be added separately from the d
43、ilution solvent as long as the internalstandard concentration is constant or accurately known.9. Sampling9.1 The objective of sampling is to obtain a test specimenthat is representative of the entire quantity. Thus, take labsamples in accordance with the instructions in Practice D 4057.The specific
44、sampling technique can affect the accuracy of thistest method.10. Preparation of Apparatus10.1 InstrumentDesign differences between instruments,ICP excitation sources, and different selected analytical wave-lengths for individual spectrometers make it impractical todetail the operating conditions. C
45、onsult the manufacturersinstructions for operating the instrument with organic solvents.Set up the instrument for use with the particular dilutionsolvent chosen.10.2 Peristaltic Pump If a peristaltic pump is used,inspect the pump tubing and replace it, if necessary, beforestarting each day. Verify t
46、he solution uptake rate and adjust itto the desired rate.10.3 ICP Excitation SourceInitiate the plasma source atleast 30 min before performing an analysis. During this warmup period, nebulize dilution solvent. Inspect the torch forcarbon build-up during the warm up period. If carbon build-upoccurs,
47、replace the torch immediately and consult the manu-facturers operating guide to take proper steps to remedy thesituation.NOTE 2Carbon that accumulates on the tip of the torch injector tubecan be removed by using nebulizer gas that consists of approximately 1 %oxygen in argon.10.3.1 Generally, carbon
48、 build-up can be minimized byincreasing the intermediate argon flow rate or lowering thetorch, or both, relative to the load coil.NOTE 3Some manufacturers recommend even longer warm up peri-ods to minimize changes in the slopes of the calibration curves.10.4 Wavelength ProfilingPerform any wavelengt
49、h profil-ing that is specified in the normal operation of the instrument.10.5 Operating ParametersAssign the appropriate oper-ating parameters to the instrument task file so that the desiredelements can be determined. Parameters to be included areelement, wavelength, background correction points (optional),interelement correction factors (refer to 5.1), integration time,and internal standard compensation (required). Multiple inte-grations (typically three) are required for each measurement. Atypical integration time is 10 s.11. Preparation of Test Specimens11.1 D
