1、Designation: D7740 11 (Reapproved 2016)Standard Practice forOptimization, Calibration, and Validation of AtomicAbsorption Spectrometry for Metal Analysis of PetroleumProducts and Lubricants1This standard is issued under the fixed designation D7740; the number immediately following the designation in
2、dicates 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers information on the
3、calibration andoperational guidance for elemental measurements using atomicabsorption spectrometry (AAS).1.1.1 AAS Related StandardsTest Methods D1318,D3237, D3340, D3605, D3831, D4628, D5056, D5184,D5863, D6732; Practices D7260 and D7455; and Test MethodsD7622 and D7623.1.2 The values stated in SI
4、units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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 p
5、ractices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1318 Test Method for Sodium in Residual Fuel Oil (FlamePhotometric Method)D3237 Test Method for Lead in Gasoline byAtomicAbsorp-tion SpectroscopyD3340 Test Method for Lithium
6、and Sodium in LubricatingGreases by Flame Photometer (Withdrawn 2013)3D3605 Test Method for Trace Metals in Gas Turbine Fuelsby Atomic Absorption and Flame Emission SpectroscopyD3831 Test Method for Manganese in Gasoline By AtomicAbsorption SpectroscopyD4057 Practice for Manual Sampling of Petroleum
7、 andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD4628 Test Method for Analysis of Barium, Calcium,Magnesium, and Zinc in Unused Lubricating Oils byAtomic Absorption Spectrometr
8、yD5056 Test Method for Trace Metals in Petroleum Coke byAtomic AbsorptionD5184 Test Methods for Determination of Aluminum andSilicon in Fuel Oils by Ashing, Fusion, InductivelyCoupled Plasma Atomic Emission Spectrometry, andAtomic Absorption SpectrometryD5863 Test Methods for Determination of Nickel
9、,Vanadium, Iron, and Sodium in Crude Oils and ResidualFuels by Flame Atomic Absorption SpectrometryD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6732 Test Method for Determination of Copper in JetFuels by
10、 Graphite Furnace Atomic Absorption Spectrom-etryD6792 Practice for Quality System in Petroleum Productsand Lubricants Testing LaboratoriesD7260 Practice for Optimization, Calibration, and Valida-tion of Inductively Coupled Plasma-Atomic EmissionSpectrometry (ICP-AES) for Elemental Analysis of Petro
11、-leum Products and LubricantsD7455 Practice for Sample Preparation of Petroleum andLubricant Products for Elemental AnalysisD7622 Test Method for Total Mercury in Crude Oil UsingCombustion and Direct Cold Vapor Atomic AbsorptionMethod with Zeeman Background CorrectionD7623 Test Method for Total Merc
12、ury in Crude Oil UsingCombustion-Gold Amalgamation and Cold Vapor AtomicAbsorption Method1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-mittee D02.03 on Elemental Analysis.Current edition ap
13、proved April 1, 2016. Published May 2016. Originallyapproved in 2011. Last previous edition approved in 2011 as D7740 11. DOI:10.1520/D7740-11R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
14、 volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1
15、 Definitions:3.1.1 absorbance, nlogarithm to the base 10 of the ratio ofthe reciprocal of the transmittance.3.1.2 atomic absorption spectrometry, nanalytical tech-nique for measuring metal content of solutions, based on acombination of flame source, hollow cathode lamp,photomultiplier, and a readout
16、 device.3.1.3 atomizer, nusually a flame source used to decom-pose the chemical constituents in a solution to its elementalcomponents.3.1.4 blank, nsolution which is similar in composition andcontents to the sample solution but does not contain the analytebeing measured.3.1.5 burner, nflame device u
17、sed to atomize the analyte byburning in a high temperature flame mixed of a fuel and anoxidant.3.1.6 calibration, nprocess by which the relationshipbetween signal intensity and elemental concentration is deter-mined for a specific element analysis.3.1.7 calibration curve, nplot of signal intensity v
18、ersuselemental concentration using data obtained by making mea-surements with standards.3.1.8 calibration standard, nmaterial with a certifiedvalue for a relevant property, issued by or traceable to anational organization such as NIST, and whose properties areknown with sufficient accuracy to permit
19、 its use to evaluate thesame property of another sample.3.1.9 certified reference material, nreference material oneor more of whose property values are certified by a technicallyvalid procedure, accompanied by a traceable certificate or otherdocumentation which is issued by a certifying body.3.1.10
20、check standard, nmaterial having an assigned(known) value (reference value) used to determine the accu-racy of the measurement system or instrument.3.1.10.1 DiscussionThis practice is not used to calibratethe measurement instrument or system.3.1.11 detection limit, nconcentration of an analyte thatr
21、esults in a signal intensity that is some multiple (typically two)times the standard deviation of the background intensity at themeasurement wavelength.3.1.12 dilution factor, nratio of sample weight of thealiquot taken to the final diluted volume of its solution.3.1.12.1 DiscussionThe dilution fact
22、or is used to multiplythe observed reading and obtain the actual concentration of theanalyte in the original sample.3.1.13 graphite furnace, nelectrothermal device for atom-izing the metal constituents.3.1.14 hollow cathode lamp, ndevice consisting of aquartz envelope containing a cathode of the met
23、al to bedetermined and a suitable anode.3.1.15 hydride generation, ndevice to atomize some met-als which form gaseous hydrides.3.1.16 monochromator, ndevice that isolates a singleatomic resonance line from the line spectrum emitted by thehollow cathode lamp, excluding all other wavelengths.3.1.17 ne
24、bulizer, ndevice that generates an aerosol byflowing a liquid over a surface that contains an orifice fromwhich gas flows at a high velocity.3.1.18 NIST, nNational Institute of Standards andTechnology, Gaithersburg, MD. Formerly known as NationalBureau of Standards.3.1.19 precision, ncloseness of ag
25、reement between testresults obtained under prescribed conditions.3.1.20 quality assurance, nsystem of activities, the pur-pose of which is to provide to the producer and user of aproduct, measurement, or service the assurance that it meetsthe defined standards of quality with a stated level of confi
26、-dence.3.1.21 quality control, nplanned system of activitieswhose purpose is to provide a level of quality that meets theneeds of users; also the uses of such a system.3.1.22 quality control sample, nfor use in quality assur-ance program to determine and monitor the precision andstability of a measu
27、rement system; a stable and homogenousmaterial having physical or chemical properties, or both,similar to those of typical samples tested by the analyticalmeasurement system.3.1.22.1 DiscussionThis material should be properlystored to ensure sample integrity, and is available in sufficientquantity f
28、or repeated long term testing.3.1.23 reference material, nmaterial with accepted refer-ence value(s), accompanied by an uncertainty at a stated levelof confidence for desired properties, which may be used forcalibration or quality control purposes in the laboratory.3.1.24 refractory elements, neleme
29、nts forming difficult-to-dissociate oxides during combustion.3.1.25 repeatability, ndifference between two test results,obtained by the same operator with the same apparatus underconstant operating conditions on identical test material would,in the long term and correct operation of the test method,
30、exceed the values given only in one case in twenty.3.1.26 reproducibility, ndifference between two singleand independent results, obtained by different operators work-ing in different laboratories on identical test materials, would inthe long run, in the normal and correct operation of the testmetho
31、d, exceed the values given only one case in twenty.3.1.27 spectrometer, ninstrument used to measure theemission or absorption spectrum emitted by a species in thevaporized sample.3.1.28 spectrum, narray of the components of an emissionor absorption arranged in the order of some varying character-ist
32、ics such as wavelength, mass, or energy.3.1.29 standard reference material, ntrademark for refer-ence materials certified by NIST.4. Summary of Practice4.1 An Atomic Absorption Spectrometer (AAS) is used todetermine the metal composition of various liquid matrices.D7740 11 (2016)2Although usually AA
33、S is done using a flame to atomize themetals, graphite furnace (GF-AAS) or cold vapor (CV-AAS)may also be used for metals at very low levels of concentrationor some elements not amenable to flame atomization. Thispractice summarizes the protocols to be followed duringcalibration and verification of
34、the instrument performance.5. Significance and Use5.1 Accurate elemental analysis of petroleum products andlubricants is necessary for the determination of chemicalproperties, which are used to establish compliance with com-mercial and regulatory specifications.5.2 Atomic Absorption Spectrometry (AA
35、S) is one of themost widely used analytical techniques in the oil industry forelemental analysis. There are at least twelve Standard TestMethods published by ASTM D02 Committee on PetroleumProducts and Lubricants for such analysis. See Table 1.5.3 The advantage of using an AAS analysis include goods
36、ensitivity for most metals, relative freedom frominterferences, and ability to calibrate the instrument based onelemental standards irrespective of their elemental chemicalforms. Thus, the technique has been a method of choice in mostof the oil industry laboratories. In many laboratories, AAS hasbee
37、n superseded by a superior ICP-AES technique (see Prac-tice D7260).5.4 Some of the ASTM AAS Standard Test Methods havealso been issued by other standard writing bodies as technicallyequivalent standards. See Table 2.6. Interferences6.1 Although over 70 elements can be determined by AASusually with a
38、 precision of 1-3 % and with detection limits ofthe order of sub-mg/kg levels, and with little or no atomicspectral interference. However, there are several types ofinterferences possible: chemical, ionization, matrix, emission,spectral, and background absorption interferences. Since theseinterferen
39、ces are well-defined, it is easy to eliminate orcompensate for them. See Table 3.6.1.1 Chemical InterferencesIf the sample for analysiscontains a thermally stable compound with the analyte that isnot totally decomposed by the energy of the flame, a chemicalinterference exists. They can normally be o
40、vercome or con-trolled by using a higher temperature flame or addition of areleasing agent to the sample and standard solutions.6.1.2 Ionization InterferencesWhen the flame has enoughenergy to cause the removal of an electron from the atom,creating an ion, ionization interference can occur. They can
41、 becontrolled by addition of an excess of an easily ionized elementto both samples and standards. Normally alkali metals whichhave very low ionization potentials are used.6.1.3 Matrix InterferencesThese can cause either a sup-pression or enhancement of the analyte signal. Matrix interfer-ences occur
42、 when the physical characteristics viscosity,burning characteristics, surface tension of the sample andstandard differ considerably. To compensate for the matrixinterferences, the matrix components in the sample and stan-dard should be matched as closely as possible. Matrix inter-ferences can also b
43、e controlled by diluting the sample solutionuntil the effect of dissolved salts or acids is negligible.Sometimes, the method of standard addition is used to over-come this interference. See 6.2.6.1.4 Emission InterferencesAt high analyteconcentrations, the atomic absorption analysis for highly emis-
44、sive elements sometimes exhibits poor analytical precision, ifthe emission signal falls within the spectral bandpass beingused. This interference can be compensated for by decreasingthe slit width, increasing the lamp current, diluting the sample,and / or using a cooler flame.6.1.5 Spectral Interfer
45、encesWhen an absorbing wave-length of an element present in the sample but not beingdetermined falls within the bandwidth of the absorption line ofthe element of interest a spectral interference can occur. Aninterference by other atoms can occur when there is a sufficientoverlapping between radiatio
46、n and emitted by the excitedatoms and other absorbing atoms. Usually the bandwidth ismuch wider than the width of the emission and absorptionlines. Thus, interferences by other atoms are fortunately quitelimited inAAS. The interference can result in erroneously highresults. This can be overcome by u
47、sing a smaller slit orselecting an alternate wavelength.6.1.6 Background Absorption InterferencesThere are twocauses of background absorption: light scattering by particlesin the flame and molecular absorption of light from the lamp bymolecules in the flame. This interference cannot be correctedwith
48、 standard addition method. The most common way tocompensate for background absorption is to use a backgroundcorrector which utilizes a continuum source.6.2 Standard Addition MethodOne way of dealing withsome of the interferences in the AAS methods is to use aTABLE 1 Applications of AAS for Metal Ana
49、lysis of Petroleum Products and LubricantsASTM Test Method Matrix Elements DeterminedD1318 Residual Fuel Oil SodiumD3237 Gasoline LeadD3340 Greases Lithium and SodiumD3605 Gas Turbine Fuels Calcium, Lead, Sodium, and VanadiumD3831 Gasoline ManganeseD4628 Automotive Lubricants Barium, Calcium, Magnesium, and ZincD5056 Petroleum Coke Aluminum, Calcium, Iron, Nickel, Silicon, Sodium, and VanadiumD5184 Fuel Oils Aluminum and SiliconD5863 Crude and Fuel Oils Iron, Nickel, Sodium, and VanadiumD6732 Jet Fuels CopperD7622 Crude Oils MercuryD7623 C
