1、Designation: D 7151 05Standard Test Method forDetermination of Elements in Insulating Oils by InductivelyCoupled Plasma Atomic Emission Spectrometry (ICP-AES)1This standard is issued under the fixed designation D 7151; the number immediately following the designation indicates the year oforiginal ad
2、option 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 describes the determination of metalsand contaminant
3、s in insulating oils by inductively coupledplasma atomic emission spectrometry (ICP-AES). The specificelements are listed in Table 1. This test method is similar toTest Method D 5185, but differs in methodology, which resultsin the greater sensitivity required for insulating oil applica-tions.1.2 Th
4、is test method uses oil-soluble metals for calibrationand does not purport to quantitatively determine insolubleparticulates. Analytical results are particle size dependent, andlow results are obtained for particles larger than severalmicrometers.21.3 This test method determines the dissolved metals
5、 (whichmay originate from overheating) and a portion of the particu-late metals (which generally originate from a wear mecha-nism). While this ICP method detects nearly all particles lessthan several micrometers, the response of larger particlesdecreases with increasing particle size because larger
6、particlesare less likely to make it through the nebulizer and into thesample excitation zone.1.4 This test method includes an option for filtering the oilsample for those users who wish to separately determinedissolved metals and particulate metals (and hence, totalmetals).1.5 Elements present at co
7、ncentrations above the upper limitof the calibration curves can be determined with additional,appropriate dilutions and with no degradation of precision.1.6 The values stated in SI (metric) units are to be regardedas the standard. The inch-pound units given in parentheses arefor information only.1.7
8、 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 to determine theapplicability of regulatory limitations prior to use.2. Referenced Doc
9、uments2.1 ASTM Standards:3C 1109 Test Method for Analysis of Aqueous Leachatesfrom Nuclear Waste Materials Using Inductively CoupledPlasma-Atomic Emission SpectrometryD 923 Practices for Sampling Electrical Insulating LiquidsD 1744 Test Method for Determination of Water in LiquidPetroleum Products b
10、y Karl Fischer ReagentD 2864 Terminology Relating to Electrical Insulating Liq-uids and GasesD 4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD 5185 Test Method for Determination of Additive Ele-ments, Wear Metals, and Contaminants in Used Lubricat-ing Oil and Determina
11、tion of Selected Elements in BaseOils by Inductively Coupled Plasma Atomic EmissionSpectrometry (ICP-AES)3. Terminology3.1 Definitions for general terms may be found in Termi-nology D 2864.3.2 Definitions of Terms Specific to This Standard:3.2.1 Babington-type nebulizera device that generates anaero
12、sol by flowing a liquid over a surface that contains anorifice from which gas flows at a high velocity.3.2.2 inductively-coupled plasma (ICP)a high-temperature discharge generated by flowing an ionizable gasthrough a magnetic field induced by a load coil that surroundsthe tubes carrying the gas.3.2.
13、3 linear response rangethe elemental concentrationrange over which the calibration curve is a straight line, withinthe precision of the test method.3.2.4 profilinga technique that determines the wavelengthfor which the signal intensity measured for a particular analyteis a maximum.3.2.5 wear metalan
14、 element introduced into the oil bywear of oil-wetted parts.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mitteeD27.03 on Analytical Tests.Current edition approved May 1, 2005. Published June 200
15、5.2Eisentraut, K. J., Newman, R. W., Saba, C. S., Kauffman, R. E., and Rhine, W.E., Analytical Chemistry, Vol 56, 1984.3For 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
16、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.3.2.6 dissolved metala metallic element in the oil whichwill pass a 0.45 filter.4. Summary of Test Method4.1 A weighed portion
17、of a thoroughly homogenized insu-lating oil is diluted 2.5:1 by weight with kerosine or othersuitable solvent. Standards are prepared in the same manner.An internal standard is added to the solutions to compensate forvariations in test specimen introduction efficiency. The solu-tions are introduced
18、to the ICP instrument by a peristalticpump. If free aspiration is used, an internal standard must beused. By comparing emission intensities of elements in the testspecimen with emission intensities measured with the stan-dards, the concentrations of elements in the test specimen arecalculated.5. Sig
19、nificance and Use5.1 This test method covers the rapid determination of 12elements in insulating oils, and it provides rapid screening ofused oils for indications of wear. Test times approximateseveral minutes per test specimen, and detectability is in the10-100 g/kg range.5.2 This test method can b
20、e used to monitor equipmentcondition and help to define when corrective action is needed.It can also be used to detect contamination such as fromsilicone fluids (via Silicon) or from dirt (via Silicon andAluminum).5.3 This test method can be used to indicate the efficiency ofreclaiming used insulati
21、ng oil.6. Interferences6.1 SpectralCheck all spectral interferences expectedfrom the elements listed in Table 1. Follow the ICP manufac-turers operating guide to develop and apply correction factorsto compensate for the interferences. To apply interferencecorrections, all concentrations must be with
22、in the previouslyestablished linear response range of each element listed inTable 1.6.1.1 Spectral interferences can usually be avoided byjudicious choice of analytical wavelengths. When spectralinterferences cannot be avoided, the necessary correctionsshould be made using the computer software supp
23、lied by theICP manufacturer or the empirical method given in TestMethod C 1109 or by Boumans.46.1.2 Interference correction factors can be negative ifoff-peak background correction is employed for an element. Anegative correction factor can result when an interfering line isencountered at the backgr
24、ound correction wavelength ratherthan at the peak wavelength.6.2 Viscosity EffectsDifferences in the viscosities of thetest specimen solutions and standard solutions can causedifferences in the uptake rates. These differences can adverselyaffect the accuracy of the analysis. The effects can be reduc
25、edby using a peristaltic pump to deliver solutions to the nebulizeror by the use of internal standardization, or both.6.3 ParticulatesThe use of an internal standard willreveal when particulates cause flow problems. Use of aBabington-type high-solids nebulizer helps to minimize plug-ging of the nebu
26、lizer. Also, the specimen introduction systemcan limit the transport of particulates, and the plasma canincompletely atomize larger particulates, thereby causing lowresults.6.4 Solvent MoistureExcessive moisture (30 mg/kg) inthe kerosine used for dilution can cause poor recovery of someelements. Thi
27、s can be minimized by checking each lot ofkerosine for moisture content using Test Method D 1744 andby analyzing all diluted standards and test specimens within 24h of preparation.7. Apparatus7.1 Balance, top loading, with automatic tare, capable ofweighing to 0.001g, capacity of at least 150 g. A b
28、alance witha capacity of at least 250 g is required if preparing the InternalStandard according to 10.2.7.2 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 maintain th
29、e plasma. Suggested wave-lengths for the determination of the elements in insulating oilare given in Table 1.7.3 NebulizerUse the nebulizer recommended by the ICPmanufacturer. A Babington-type4high-solids nebulizer may beuseful if samples contain high solids. This type of nebulizerreduces the possib
30、ility of clogging and minimizes aerosolparticle effects.7.4 Peristaltic PumpA peristaltic pump is required toprovide a constant flow of solution. The pump tubing must beable to withstand at least 6 h exposure to the dilution solvent.Viton tubing is typically used with hydrocarbon solvents, andpoly (
31、vinyl chloride) tubing is typically used with methylisobutyl ketone.7.5 Solvent Dispenser, (optional) A solvent dispensercalibrated to deliver the required weight of dilution solvent isvery useful. This dispenser should have at least 1 % accuracyand 0.1 % precision.7.6 Internal Standard Dispenser, (
32、Optional) A dispensercalibrated to deliver the required weight of internal standard4Boumans, P. W .J. M., “Corrections for Spectral Interferences in OpticalEmission Spectroscopy with Special Reference to the RF Inductively CoupledPlasma,” Spectrochimica Acta, 1976, Vol 318, pp. 147-152.TABLE 1 Eleme
33、nts Determined and Suggested WavelengthsAElement Wavelength, nmAluminum 308.22, 396.15, 309.27Cadmium 226.50. 214.44Cobalt 228.62 231.16Copper 324.75Iron 259.94, 238.20Lead 220.35Nickel 231.60, 227.02, 221.65Scandium 361.38Silicon 288.16, 251.61Silver 328.07Sodium 589.59Tin 189.99, 242.95Tungsten 23
34、9.71Yttrium 371.03Zinc 206.20, 202.55, 213.86, 334.58, 481.05AThese wavelengths are only suggested and do not represent all possiblechoices.D7151052solution is very useful. This dispenser should have at least 1 %accuracy and 0.1 % precision.7.7 Specimen Solution Containers, nominal 30 mL (1 oz.),gla
35、ss or plastic vials, with screw caps or snap-top caps.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 Che
36、mical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without introducing a significantsource of error.8.2 Base OilU.S.P. White oil or any mineral oil that is freeof analytes an
37、d having a viscosity at room temperature as closeas possible to that of the samples to be analyzed.8.3 Internal StandardOil-soluble scandium, cobalt, oryttrium is required when the internal standardization option isselected.8.4 Organometallic StandardsMulti-element standards,containing 3.0 and 10.0
38、g/g of each element, can be purchasedor prepared from the individual concentrates. Refer to PracticeD 4307 for a procedure for preparation of multicomponentliquid blends. When preparing multi-element standards, anultrasonic bath is recommended to ensure that complete mixingis achieved. It is highly
39、recommended to purchase the stan-dards because of the difficulty in preparing multi-elementstandards.8.5 Dilution SolventReagent grade kerosine is recom-mended as a dilution solvent. Another solvent (such as tolueneor xylene) may be used if it is free of all analytes andcompletely dissolves all stan
40、dards and samples.9. Hazards9.1 Kerosine is classified as a combustible liquid and mustbe kept away from all ignition sources. If the ICP is allowed tooperate unattended, equipment malfunctions could cause leak-age of kerosine.10. Internal Standardization10.1 The internal standard procedure requires
41、 that every testspecimen solution have the same concentration of an internalstandard element that is not present in the original specimen.Specimen to specimen changes in the emission intensity of theinternal standard element can be used to correct for variationsin the test specimen introduction effi
42、ciency, which is dependenton the physical properties of the test specimen.10.2 Internal Standard SolutionWeigh 25.0 6 0.1g of2000 g/g scandium-in-oil (or cobalt- or yttrium-in-oil) stan-dard into a 500-mL Erlenmeyer flask. Add kerosine to make atotal of 250 6 1 g. Mix this solution thoroughly and tr
43、ansfer tothe reservoir for the internal standard container or dispenser.The concentration of the internal standard is not required to be200 g/g. However, the concentration of the internal standardelement should be at least 100 times its detection limit.11. Sampling and Sample Handling11.1 Laboratory
44、 samples must be taken in accordance withthe instructions in Practices D 923.11.2 It is important to homogenize the insulating oil in thesample container in order to obtain a representative testspecimen. Mix the insulating oil sample vigorously by invert-ing several times.11.3 (Optional) To separate
45、ly determine the dissolved met-als and particulate metals, filter the oil sample through a 0.45 filter. The particles on the filter paper must then be dissolvedor digested by a technique not addressed by this test method.12. Preparation of Test Specimens and Standards12.1 All test specimens and stan
46、dards must be mixedthoroughly when diluted with kerosine and the internal stan-dard. They must all be prepared from the same batch of internalstandard. All prepared solutions must be analyzed within 24 hof preparation.12.2 BlankPrepare a blank by adding 6.00 6 0.02 g baseoil, 1.00 6 0.01 g internal
47、standard solution, and 8.00 6 0.03g kerosine to a 30-mL polyethylene or glass vial.12.3 Working StandardPrepare a calibration standard byadding 6.00 6 0.02 g of the 10 g/g multi-element standard,1.00 6 0.01 g internal standard solution, and 8.00 6 0.03 gkerosine to a 30-mL polyethylene vial.12.4 Che
48、ck StandardPrepare a QC check standard byadding 6.00 6 0.02 g of the 3.0 g/g multi-element standard,1.00 6 0.01 g internal standard solution, and 8.00 6 0.03 gkerosine. Other concentrations may be used for the checkstandard as long as they are not prepared from the 10 g/gstandard used for calibratio
49、n.12.5 Test SpecimenAdd 6.00 6 0.02 g of a well-homogenized sample, 1.00 6 0.01 g internal standard solution,and 8.00 6 0.03 g kerosine to a 30-mL polyethylene vial. If theanalysis report indicates a concentration above the linear range,prepare a 10-fold dilution by adding 0.60 6 0.01 g of thesample, 5.40 6 0.02 g base oil, 1.00 6 0.01 g internal standardsolution, and 8.00 6 0.03 g kerosine to a 30-mL polyethylenevial. Identify the sample as a 10X dilution and ensure that theinstrument software will correct the concentrations for theadditional dilut
