1、Designation: D7151 15Standard Test Method forDetermination of Elements in Insulating Oils by InductivelyCoupled Plasma Atomic Emission Spectrometry (ICP-AES)1This standard is issued under the fixed designation D7151; the number immediately following the designation indicates the year oforiginal adop
2、tion or, 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. Scope1.1 This test method describes the determination of metalsand contaminants i
3、n insulating oils by inductively coupledplasma atomic emission spectrometry (ICP-AES). The specificelements are listed in Table 1. This test method is similar toTest Method D5185, but differs in methodology, which resultsin the greater sensitivity required for insulating oil applica-tions.1.2 This t
4、est 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 (wh
5、ichcan originate from overheating or arcing, or both) and a portionof the particulate metals (which generally originate from awear mechanism). While this ICP method detects nearly allparticles less than several micrometers, the response of largerparticles decreases with increasing particle size beca
6、use largerparticles are less likely to make it through the nebulizer andinto the sample 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 pr
7、esent at concentrations 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 units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This sta
8、ndard 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 Documents2.1
9、 ASTM Standards:3C1109 Practice for Analysis of Aqueous Leachates fromNuclear Waste Materials Using Inductively CoupledPlasma-Atomic Emission SpectroscopyD923 Practices for Sampling Electrical Insulating LiquidsD1744 Test Method for Water in Liquid Petroleum Productsby Karl Fischer Reagent4D2864 Ter
10、minology Relating to Electrical Insulating Liq-uids and GasesD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD5185 Test Method for Multielement Determination ofUsed and Unused Lubricating Oils and Base Oils byInductively Coupled Plasma Atomic Emission Spectrom-etry (ICP
11、-AES)E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions for general terms are found in TerminologyD2864.3.2 Definitions of Terms Specific to This Standa
12、rd:3.2.1 Babington-type nebulizer, na device that generatesan aerosol 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), na high-temperature discharge generated by flowing an ionizable gasthrough a magnetic field
13、 induced by a load coil that surroundsthe tubes carrying the gas.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, 2015. Published Jun
14、e 2015. Originallyapproved in 2005. Last previous edition approved in 2013 as D7151-13. DOI:10.1520/D7151-15.2Eisentraut, 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, orco
15、ntact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.Copyright ASTM International, 100 Barr H
16、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.3 linear response range, nthe elemental concentrationrange over which the calibration curve is a straight line, withinthe precision of the test method.3.2.4 profiling, na technique that determines the wave-length for which
17、 the signal intensity measured for a particularanalyte is a maximum.3.2.5 wear metal, nan element introduced into the oil bywear of oil-wetted parts.3.2.6 dissolved metal, na metallic element in the oil whichwill pass a 0.45 m filter.4. Summary of Test Method4.1 A weighed portion of a thoroughly hom
18、ogenized insu-lating oil is diluted by weight with kerosine or other suitablesolvent. Standards are prepared in the same manner. Aninternal standard may be added to the solutions to compensatefor variations in test specimen introduction efficiency. Thesolutions may be introduced to the ICP instrumen
19、t by aperistaltic pump. If free aspiration is used, an internal standardshall be used. By comparing emission intensities of elements inthe test specimen with emission intensities measured with thestandards, the concentrations of elements in the test specimenare calculated.5. Significance and Use5.1
20、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 the 10through 100 g/kg range.5.2 This test method can be used to mon
21、itor 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 insulating oil.6. Int
22、erferences6.1 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 within the previo
23、uslyestablished 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 corrections shallbe made using the computer software supplied by the IC
24、Pmanufacturer or the empirical method given in Test MethodC1109 or by Boumans.56.1.2 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 background correction
25、 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 reducedby using a pe
26、ristaltic pump to deliver solutions to the nebulizeror by the use of internal standardization, or both.6.3 ParticulatesThe use of an internal standard will revealwhen particulates cause flow problems. Use of a Babington-type high-solids nebulizer helps to minimize plugging of thenebulizer. Also, the
27、 specimen introduction system can limit thetransport of particulates, and the plasma can incompletelyatomize larger particulates, thereby causing low results.6.4 Solvent MoistureExcessive moisture (30 mg/kg) inthe kerosine used for dilution can cause poor recovery of someelements. This can be minimi
28、zed by checking each lot ofkerosine for moisture content using Test Method D1744 and byanalyzing all diluted standards and test specimens within 24 hof preparation.7. Apparatus7.1 Balance, top loading, with automatic tare, capable ofweighing to 0.001g, capacity of at least 150 g. A balance witha cap
29、acity 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 the plasma. Sugges
30、ted 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-type high-solids nebulizer shouldbe used if samples contain high solids. This type of nebulizerreduces the possibility of cloggi
31、ng and minimizes aerosolparticle effects.7.4 Peristaltic Pump, (optional)Aperistaltic pump may beused to provide a constant flow of solution. The pump tubing5Boumans, P. W .J. M., “Corrections for Spectral Interferences in OpticalEmission Spectroscopy with Special Reference to the RF Inductively Cou
32、pledPlasma,” Spectrochimica Acta, 1976, Vol 318, pp. 147-152.TABLE 1 Elements 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 361.38Sil
33、icon 288.16, 251.61Silver 328.07Sodium 589.59Tin 189.99, 242.95Tungsten 239.71Yttrium 371.03Zinc 206.20, 202.55, 213.86, 334.58, 481.05AThese wavelengths are only suggested and do not represent all possible choices.D7151 152shall be able to withstand at least 6 h exposure to the dilutionsolvent. Vit
34、on tubing is typically used with hydrocarbonsolvents, and poly (vinyl chloride) tubing is typically used withmethyl isobutyl ketone.7.5 Solvent Dispenser (optional), A solvent dispensercalibrated to deliver the required weight of dilution solvent isvery useful. This dispenser shall have at least 1 %
35、 accuracy and0.1 % precision.7.6 Internal Standard Dispenser (optional), A dispensercalibrated to deliver the required weight of internal standardsolution is very useful. This dispenser shall have at least 1 %accuracy and 0.1 % precision.7.7 Specimen Solution Containers, nominal 30-mL glass orpolyet
36、hylene 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 Chemical S
37、ociety wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofdetermination.8.2 Base OilU.S.P. White oil or any mineral oil that is freeof analytes and having
38、a viscosity at room temperature as closeas possible to that of the samples to be analyzed.8.3 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 standards and s
39、amples.8.4 Internal StandardOil-soluble scandium, cobalt, oryttrium is required when the internal standardization option isselected.8.5 Organometallic StandardsMulti-element standards,containing 3.0 and 10.0 mg/kg of each element, can bepurchased or prepared from the individual concentrates. Referto
40、 Practice D4307 for a procedure for preparation of multicom-ponent liquid blends. When preparing multi-element standards,an ultrasonic bath is recommended to ensure that completemixing is achieved. It is highly recommended to purchase thestandards because of the difficulty in preparing multi-element
41、standards.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 that ev
42、ery 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 efficiency,
43、which is dependenton the physical properties of the test specimen.10.2 Internal Standard Solution Weigh 25.0 6 0.1g of2000 mg/kg scandium-in-oil (or cobalt- or yttrium-in-oil)standard into a 500-mL Erlenmeyer flask. Add kerosine tomake a total of 250 6 1 g. Mix this solution thoroughly andtransfer t
44、o the reservoir for the internal standard container ordispenser. The concentration of the internal standard is notrequired to be 200 mg/kg. However, the concentration of theinternal standard element should be at least 100 times itsdetection limit.11. Sampling and Sample Handling11.1 Laboratory sampl
45、es must be taken in accordance withthe instructions in Practices D923.11.2 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 separately dete
46、rmine the dissolved met-als and particulate metals, filter the oil sample through a 0.45m filter. The particles on the filter paper must then bedissolved or digested by a technique not addressed by this testmethod.12. Preparation of Test Specimens and Standards12.1 All test specimens and standards m
47、ust be mixedthoroughly when diluted with kerosine and the internal stan-dard. They must all be prepared utilizing the same batch ofinternal standard. All prepared solutions must be analyzedwithin 24 h of preparation.12.2 BlankPrepare a blank by adding 6.00 6 0.02 g baseoil, 1.00 6 0.01 g internal st
48、andard solution, and 8.00 6 0.03g kerosine to a 30-mL vial.12.3 Working StandardPrepare a calibration standard byadding 6.00 6 0.02 g of the 10 mg/kg multi-element standard,1.00 6 0.01 g internal standard solution, and 8.00 6 0.03 gkerosine to a 30-mL vial.12.4 Check StandardPrepare a QC check stand
49、ard byadding 6.00 6 0.02 g of the 3.0 mg/kg multi-element standard,1.00 6 0.01 g internal standard solution, and 8.00 6 0.03 gkerosine to a 30-mL vial. Other concentrations may be used forthe check standard as long as they are not prepared from the 10mg/kg standard used for calibration.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 vial. If the analysisreport indicates a concentration above the linear range, preparea 10-fold dilution by adding 0.60 6 0.01 g
