1、Designation: D 7303 06An American National StandardStandard Test Method forDetermination of Metals in Lubricating Greases byInductively Coupled Plasma Atomic Emission Spectrometry1This standard is issued under the fixed designation D 7303; the number immediately following the designation indicates t
2、he 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.1. Scope1.1 This test method covers the determination of a n
3、umberof metals such as aluminum, antimony, barium, calcium, iron,lithium, magnesium, molybdenum, phosphorus, silicon, so-dium, sulfur, and zinc in unused lubricating greases by induc-tively coupled plasma atomic emission spectrometry (ICP-AES) technique.1.1.1 The range of applicability for this test
4、 method, basedon the interlaboratory study conducted in 2005,2is aluminum(10600), antimony (102300), barium (50800), calcium(2050 000), iron (10360), lithium (3003200), magnesium(3010 000), molybdenum (5022 000), phosphorus(502000), silicon (1015 000), sodium (301500), sulfur(160028 000), and zinc (
5、3002200), all in mg/kg. Lowerlevels of elements may be determined by using larger sampleweights, and higher levels of elements may be determined byusing smaller amounts of sample or by using a larger dilutionfactor after sample dissolution. However, the test precision insuch cases has not been deter
6、mined, and may be different thanthe ones given in Table 1.1.1.2 It may also be possible to determine additional metalssuch as bismuth, boron, cadmium, chromium, copper, lead,manganese, potassium, titanium, etc. by this technique. How-ever, not enough data is available to specify the precision forthe
7、se latter determinations. These metals may originate intogreases through contamination or as additive elements.1.1.3 During sample preparation, the grease samples aredecomposed with a variety of acid mixture(s). It is beyond thescope of this test method to specify appropriate acid mixturesfor all po
8、ssible combination of metals present in the sample.But if the ash dissolution results in any visible insolublematerial, the test method may not be applicable for the type ofgrease being analyzed, assuming the insoluble material con-tains some of the analytes of interest.1.2 Elements present at conce
9、ntrations above the upper limitof the calibration curves can be determined with additionalappropriate dilutions of dissolved samples and with no degra-dation of precision.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4
10、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 regulatory limitations prior to use. Specific warningst
11、atements are given in Sections 8 and 10.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reagent WaterD 3340 Test Method for Lithium and Sodium in LubricatingGreases by Flame PhotometerD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4951 Test Method for Det
12、ermination of Additive Ele-ments in Lubricating Oils by Inductively Coupled PlasmaAtomic Emission SpectrometryD 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
13、Plasma Atomic EmissionSpectrometry (ICP-AES)D 6299 Practice for Applying Statistical Quality AssuranceTechniques to Evaluate Analytical Measurement SystemPerformance1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility
14、of SubcommitteeD02.03 on Elemental Analysis.Current edition approved Nov. 1, 2006. Published December 2006.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D021608.3For referenced ASTM standards, visit the ASTM website, www.astm.
15、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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D 6792 Guid
16、e for Quality System in Petroleum Productsand Lubricants Testing Laboratories3. Terminology3.1 DefinitionsRefer to terminology identified in TestMethod D 5185 for spectroscopy terms used in this standard.4. Summary of Test Method4.1 A weighed portion of the grease sample is weighed andsubjected to a
17、lternate means of sample dissolution which mayinclude sulfated ashing in a muffle furnace or by closed vesselmicrowave digestion in acid. Ultimately these diluted acidsolutions are analyzed using ICP-AES. Aqueous calibrationstandards are used. The solutions are introduced to the ICPinstrument by fre
18、e aspiration or an optional peristaltic pump.By comparing emission intensities of elements in the testspecimen with those measured with the calibration standards,the concentrations of elements in the test specimen can becalculated.5. Significance and Use5.1 Lubricating greases are used in almost all
19、 bearings usedin any machinery. Lubricating grease is composed of 90 %additized oil and soap or other thickening agent. There are overa dozen metallic elements present in greases, either blended asadditives for performance enhancements or as thickeners, or inused greases present as contaminants and
20、wear metals. Deter-mining their concentrations can be an important aspect ofgrease manufacture. The metal content can also indicate theamount of thickeners in the grease. Additionally, a reliableanalysis technique can also assist in the process of troubleshooting problems with new and used grease in
21、 the field.5.2 Although widely used in other sectors of the oil industryfor metal analysis, ICP-AES based Test Methods D 4951 orD 5185 cannot be used for analyzing greases because of theirinsolubility in organic solvents used in these test methods.Hence, grease samples need to be brought into aqueou
22、ssolution by acid decomposition before ICP-AES measure-ments.5.3 Test Method D 3340 has been used to determine lithiumand sodium content of lubricating greases using flame photom-etry. This technique is no longer widely used. This new testmethod provides a test method for multi-element analysis ofgr
23、ease samples. This is the first DO2 standard available forsimultaneous multi-element analysis of lubricating greases.6. Interferences6.1 SpectralSpectral interferences can usually be avoidedby judicious choice of analytical wavelengths. There are noknown spectral interferences between elements cover
24、ed by thistest method when using the spectral lines listed in Table 2.However, if spectral interferences exist because of otherinterfering elements or selection of other spectral lines, correctfor the interferences using the technique described in TestMethod D 5185.6.1.1 Follow the instrument manufa
25、cturers operating guideto develop and apply correction factors to compensate for theinterferences.6.2 ChemicalIf the grease sample contains refractoryadditives such as silicon or molybdenum, it is possible thatsome of these elements may remain undissolved in the residue,and may result in lower recov
26、eries.6.2.1 If HF is used for dissolution of grease residues,elements such as silicon may be lost as SiF6. Residual HF canalso attack the ICP sample introduction system. HF can bepassivated by adding dilute boric acid to the acid solution.6.2.2 If the dry ashing in sample preparation step is used,el
27、ements such as sulfur will be volatilized during combustion.7. Apparatus7.1 Analytical Balance, capable of weighing to 0.001 g or0.0001 g, capacity of 150 g.7.2 Inductively Coupled Plasma Atomic EmissionSpectrometerEither a sequential or simultaneous spectrom-eter is suitable, if equipped with a qua
28、rtz ICP torch and RFgenerator to form and sustain the plasma. Suggested wave-lengths for the determination of elements in dissolved greasesolutions are given in Table 2.7.3 Peristaltic Pump, (Recommended)A peristaltic pumpis strongly recommended to provide a constant flow of solu-tion. The pumping s
29、peed must be in the range of 0.5 to3 mL/min. The pump tubing must be able to withstand at least6 h exposure to solutions.TABLE 1 Precision of Grease AnalysisNOTEX is the mean concentration in mg/kg.ElementRange,mg/kgRepeatability ReproducibilityAluminum 10600 0.2163 X0.96.8156 X0.9Antimony 102300 0.
30、3051 X0.81914.6809 X0.8191Barium 50800 0.3165 X0.75282.9503 X0.7528Calcium 2050 000 2.2853 X0.70673.0571 X0.7067Iron 10360 0.8808 X0.74752.5737 X0.7475Lithium 3003200 0.0720 X1.03520.1476 X1.0352Magnesium 3010 000 0.6620 X0.68132.6155 X0.6813Molybdenum 5022 000 0.1731 X0.94740.4717 X0.9474Phosphorus
31、 502000 1.2465 X0.67404.0758 X0.6740Silicon 1015 000 1.3859 X0.99354.8099 X0.9935Sodium 301500 6.5760 X0.511.571 X0.5Sulfur 160028 000 1.0507 X0.85881.5743 X0.8588Zinc 3002200 0.1904 X0.86070.5912 X0.8607TABLE 2 Suggested WavelengthsA,Bfor Elements Determined inGrease SamplesElement Wavelength, nmAl
32、uminum 167.038, 308.22, 396.15, 309.27Antimony 206.83, 217.58, 231.15Barium 223.53, 233.527, 455.40, 493.41Calcium 315.88, 317.93, 364.4, 396.85, 422.67Iron 238.20, 259.94Lithium 670.78, 610.36, 460.29Magnesium 279.08, 279.55, 280.278, 285.21Molybdenum 135.387, 202.03, 281.62Phosphorus 177.51, 178.2
33、9, 213.62, 214.91, 253.40Silicon 288.16, 251.618Sodium 589.595Sulfur 182.04, 180.73, 182.63Zinc 202.55, 206.20, 213.86, 334.58, 481.05AThese wavelengths are only suggested and do not represent all possiblechoices.BWavelengths for boron, phosphorus, and sulfur below 190 nm require that avacuum or ine
34、rt gas purge optical path be used.D73030627.4 Specimen Solution Containers, of appropriate size, glassor polyolefin vials or bottles, with screw caps without metalliners.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it i
35、s intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without
36、 lessening the accuracy ofthe determination.8.2 Sulfuric Acid, concentrated sulfuric acid, H2SO4.(WarningCauses severe burns. Corrosive.)8.3 Nitric Acid, concentrated nitric acid, HNO3.(WarningCauses severe burns. Corrosive.)8.4 Hydrochloric Acid, concentrated hydrochloric acid,HCl. (WarningCauses b
37、urns.)8.5 Hydrofluoric Acid, concentrated hydrofluoric acid, HF(WarningCauses severe burns.)8.6 Aqueous Standard Solutions, individual aqueous el-emental standards with 100 mg/Lconcentrations of elements ofinterest. These can be prepared by dissolving pure metalcompounds in water or dilute acids, or
38、 may be purchased fromcommercial sources.8.6.1 Multi-element aqueous standards may be advanta-geous to use.8.6.2 Internal Standard, aqueous cobalt, indium, scandium,yttrium or other single element standard, not a component ofthe grease test specimen or calibration standard, nominal 500mg/kg concentr
39、ation.8.7 Water, distilled or deionized water, unless otherwiseindicated, references to water shall be understood to mean TypeII reagent grade water as defined in Specification D 1193.8.8 Quality Control (QC) Samples, preferably are portionsof one or more grease materials that are stable and represe
40、n-tative of the samples of interest. These QC samples can be usedto check the validity of the testing process as described inSection 15.8.9 Microwave Oven, commercially available laboratorymicrowave digestion oven of sufficient power (for example, atleast 1000 W) is suitable. The microwave digestion
41、 dishes arealso commercially available. (WarningTake all necessaryprecautions to prevent exposure to radiofrequency radiation.)8.10 Microwave Sample Digestion System, with closed-vessel silicon-free polytetrafluoroethylene (PTFE) digestionvessels. The vessels need to be capable of withstanding thepr
42、essure generated from the digestion of 0.2 g of sample(pressure achieved with a 100 mL vessel and 0.2 g of samplecould be in excess of 100 psi). Microwave digestions systemswith temperature and pressure monitoring are recommendedfor safety and accuracy of sample preparation.8.11 The test method requ
43、ires essentially microwave trans-parent and reagent resistant suitably inert polymeric materials(examples are PFA or TFM) to contain acids and samples. Forhigher pressure capabilities the vessel may be contained withinlayers of different microwave transparent materials forstrength, durability, and s
44、afety. The vessels internal volumeshould be at least 45 mL, capable of withstanding pressures ofat least 30 atm (30 bar or 435 psi), and capable of controlledpressure relief. These specifications are given to provide anappropriate, safe, and durable reaction vessel of which thereare many adequate de
45、signs by many suppliers.8.12 Rotating Turntable, to insure homogeneous distribu-tion of microwave radiation within most systems. The speed ofthe turntable should be a minimum of 3 rpm.8.13 Combustion Dishes, Vycor or platinum evaporationdishes of 250 mL size.8.14 Volumetric Flasks, polypropylene or
46、similar materialof 25 and 50 mL sizes.8.15 Electric Muffle Furnace, capable of maintaining 525 625C and sufficiently large to accommodate several 250 mLbeakers. The capacity of an oxygen bleed is advantageous andoptional. (WarningTake all necessary precautions to preventexposure to very hot surfaces
47、.)8.16 Heating Lamp, commercial infrared heating lamp.9. Sampling9.1 The objective of sampling is to obtain a test specimenthat is representative of the entire quantity. Thus, take labora-tory samples in accordance with the instructions in PracticeD 4057. The specific sampling technique can affect t
48、he accu-racy of this test method.10. Preparation of Samples10.1 Sulfated Ash Digestion:10.1.1 Accurately weigh approximately 1 to 2 6 0.1 g of thegrease sample in a Vycor or platinum container of suitable size.Char the sample on a hot plate until it is reduced to 0.5 g. Aheat lamp may be used to ass
49、ist in this process.10.1.2 After the charred residue is cooled, add 1 to 2 mL ofconcentrated sulfuric acid and carefully heat on the hot platetaking care to avoid spattering of the contents, and continueheating until the fumes are no longer evolved.10.1.3 Place the charred sample in a muffle furnace at 525 625C until the oxidation of the carbon is practically complete.This typically takes about 2 h.10.1.4 If the ashing is not complete as indicated by presenceof black color of the residue, repeat step 10.1.2 to complete thesulfation.10.1.5 Add
