1、Designation: D7303 12Standard Test Method forDetermination of Metals in Lubricating Greases byInductively Coupled Plasma Atomic Emission Spectrometry1This standard is issued under the fixed designation D7303; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, 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*1.1 This test method covers the determination of a numberof metals such as aluminum
3、, 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 method, basedon the interlabor
4、atory 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 (3002200), all in mg/kg. Lowerle
5、vels 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 determined, and may be different tha
6、nthe 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 forthese latter determinations. These
7、 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 possible combination of metals pr
8、esent 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 concentrations above the upper limit
9、of 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 This standard does not purport
10、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 warningstatements are given in Sections
11、8 and 10.2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD3340 Test Method for Lithium and Sodium in LubricatingGreases by Flame PhotometerD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4951 Test Method for Determination of Additive Ele-ments in
12、 Lubricating Oils by Inductively Coupled PlasmaAtomic Emission SpectrometryD5185 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 EmissionSpectrometry (
13、ICP-AES)D6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing LaboratoriesD7260 Practice for Optimization, Calibration, and Valida-tion
14、 of Inductively Coupled Plasma-Atomic EmissionSpectrometry (ICP-AES) for Elemental Analysis of Petro-leum Products and Lubricants1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental A
15、nalysis.Current edition approved June 1, 2012. Published August 2012. Originallyapproved in 2006. Last previous edition approved in 2006 as D730306. DOI:10.1520/D7303-12.2Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1608.3
16、For referenced ASTM standards, visit the ASTM website, www.astm.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.1*A Summary of Changes section appears at the end of this stan
17、dard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 DefinitionsRefer to terminology identified in TestMethod D5185 for spectroscopy terms used in this standard.4. Summary of Test Method4.1 A weighed portion of the g
18、rease sample is weighed andsubjected to alternate 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 a
19、re introduced to the ICPinstrument by free 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.4.2 Additional information o
20、n using inductively coupledplasma-atomic emission spectrometry can be found in PracticeD7260.5. Significance and Use5.1 Lubricating greases are used in almost all bearings usedin any machinery. Lubricating grease is composed of 90 %additized oil and soap or other thickening agent. There are overa do
21、zen metallic elements present in greases, either blended asadditives for performance enhancements or as thickeners, or inused greases present as contaminants and wear metals. Deter-mining their concentrations can be an important aspect ofgrease manufacture. The metal content can also indicate theamo
22、unt of thickeners in the grease. Additionally, a reliableanalysis technique can also assist in the process of troubleshooting problems with new and used grease in the field.5.2 Although widely used in other sectors of the oil industryfor metal analysis, ICP-AES based Test Methods D4951 orD5185 canno
23、t be used for analyzing greases because of theirinsolubility in organic solvents used in these test methods.Hence, grease samples need to be brought into aqueoussolution by acid decomposition before ICP-AES measure-ments.5.3 Test Method D3340 has been used to determine lithiumand sodium content of l
24、ubricating greases using flame photom-etry. This technique is no longer widely used. This new testmethod provides a test method for multi-element analysis ofgrease samples. This is the first DO2 standard available forsimultaneous multi-element analysis of lubricating greases.6. Interferences6.1 Spec
25、tralSpectral interferences can usually be avoidedby judicious choice of analytical wavelengths. There are noknown spectral interferences between elements covered by thistest method when using the spectral lines listed in Table 2.However, if spectral interferences exist because of otherinterfering el
26、ements or selection of other spectral lines, correctfor the interferences using the technique described in TestMethod D5185.6.1.1 Follow the instrument manufacturers operating guideto develop and apply correction factors to compensate for theinterferences.6.2 ChemicalIf the grease sample contains re
27、fractoryadditives such as silicon or molybdenum, it is possible thatsome of these elements may remain undissolved in the residue,and may result in lower recoveries.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
28、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,elements such as sulfur will be volatilized during combustion.7. Apparatus7.1 Analytical Balance, capable of weighing to 0.001 g or0.0001 g, cap
29、acity of 150 g.7.2 Inductively Coupled Plasma Atomic EmissionSpectrometerEither a sequential or simultaneous spectrom-eter is suitable, if equipped with a quartz ICP torch and RFgenerator to form and sustain the plasma. Suggested wave-lengths for the determination of elements in dissolved greasesolu
30、tions 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 speed 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
31、Grease AnalysisNOTEX is the mean concentration in mg/kg.ElementRange,mg/kgRepeatability ReproducibilityAluminum 10600 0.2163 X0.96.8156 X0.9Antimony 102300 0.3051 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 X0.74752.573
32、7 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 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
33、X0.85881.5743 X0.8588Zinc 3002200 0.1904 X0.86070.5912 X0.8607TABLE 2 Suggested WavelengthsA,Bfor Elements Determined inGrease SamplesElement Wavelength, nmAluminum 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.
34、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, 178.29, 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 w
35、avelengths are only suggested and do not represent all possiblechoices.BWavelengths for boron, phosphorus, and sulfur below 190 nm require that avacuum or inert gas purge optical path be used.D7303 1227.4 Specimen Solution Containers, of appropriate size, glassor polyolefin vials or bottles, with sc
36、rew caps without metalliners.8. Reagents and Materials8.1 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 s
37、pecifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Sulfuric Acid, concentrated sulfuric acid, H2SO4.(WarningCauses severe burns. Corrosive.)8.3
38、Nitric Acid, concentrated nitric acid, HNO3.(WarningCauses severe burns. Corrosive.)8.4 Hydrochloric Acid, concentrated hydrochloric acid,HCl. (WarningCauses burns.)8.5 Hydrofluoric Acid, concentrated hydrofluoric acid, HF(WarningCauses severe burns.)8.6 Aqueous Standard Solutions, individual aqueou
39、s el-emental standards with 100 mg/Lconcentrations of elements ofinterest. These can be prepared by dissolving pure metalcompounds in water or dilute acids, or may be purchased fromcommercial sources.8.6.1 Multi-element aqueous standards may be advanta-geous to use.8.6.2 Internal Standard, aqueous c
40、obalt, indium, scandium,yttrium or other single element standard, not a component ofthe grease test specimen or calibration standard, nominal 500mg/kg concentration.8.7 Water, distilled or deionized water, unless otherwiseindicated, references to water shall be understood to mean TypeII reagent grad
41、e water as defined in Specification D1193.8.8 Quality Control (QC) Samples, preferably are portionsof one or more grease materials that are stable and represen-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 Mi
42、crowave Oven, commercially available laboratorymicrowave digestion oven of sufficient power (for example, atleast 1000 W) is suitable. The microwave digestion dishes arealso commercially available. (WarningTake all necessaryprecautions to prevent exposure to radiofrequency radiation.)8.10 Microwave
43、Sample Digestion System, with closed-vessel silicon-free polytetrafluoroethylene (PTFE) digestionvessels. The vessels need to be capable of withstanding thepressure 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
44、). Microwave digestions systemswith temperature and pressure monitoring are recommendedfor safety and accuracy of sample preparation.8.11 The test method requires essentially microwave trans-parent and reagent resistant suitably inert polymeric materials(examples are PFA or TFM) to contain acids and
45、 samples. Forhigher pressure capabilities the vessel may be contained withinlayers of different microwave transparent materials forstrength, durability, and safety. The vessels internal volumeshould be at least 45 mL, capable of withstanding pressures ofat least 30 atm (30 bar or 435 psi), and capab
46、le of controlledpressure relief. These specifications are given to provide anappropriate, safe, and durable reaction vessel of which thereare many adequate designs by many suppliers.8.12 Rotating Turntable, to insure homogeneous distribu-tion of microwave radiation within most systems. The speed oft
47、he 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 similar materialof 25 and 50 mL sizes.8.15 Electric Muffle Furnace, capable of maintaining 525 625C and sufficiently large to accommodate seve
48、ral 250 mLbeakers. The capacity of an oxygen bleed is advantageous andoptional. (WarningTake all necessary precautions to preventexposure to very hot surfaces.)8.16 Heating Lamp, commercial infrared heating lamp.9. Sampling9.1 The objective of sampling is to obtain a test specimenthat is representat
49、ive of the entire quantity. Thus, take labora-tory samples in accordance with the instructions in PracticeD4057. The specific sampling technique can affect the 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 assist in this process.10.1.2 After the charred residue is cooled, add 1 to 2 mL ofconcentrat
