1、Designation: D7740 11Standard 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 indicates the year o
2、foriginal 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 calibration andope
3、rational 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 units are to be re
4、garded 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 practices and deter
5、mine 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 by Atomic Ab-sorption SpectroscopyD3340 Test Method for Lithium and Sodium in Lu
6、bricatingGreases by Flame PhotometerD3605 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 andPetroleum ProductsD4177 Practi
7、ce 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 SpectrometryD5056 Test Method for Trace Metal
8、s 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, Vana-dium, Iron, and Sodium in C
9、rude Oils and Residual Fuelsby 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 Graphite Furnace Atomic Absorpt
10、ion 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-leum Products and LubricantsD74
11、55 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 Mercury in Crude Oil UsingCombustion
12、-Gold Amalgamation and Cold Vapor AtomicAbsorption Method1This practice is under the jurisdiction of ASTM Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.03 onElemental Analysis.Current edition approved July 1, 2011. Published August 2011. DOI:
13、10.1520/D774011.2For 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.1Copyright ASTM International, 100 Barr Harbo
14、r Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 Definitions:3.1.1 absorbance, nlogarithm to the base 10 of the ratioof the reciprocal of the transmittance.3.1.2 atomic absorption spectrometry, nanalytical tech-nique for measuring metal content of solutions, ba
15、sed on acombination of flame source, hollow cathode lamp, photomul-tiplier, and a readout 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 compositionand contents to the sam
16、ple solution but does not contain theanalyte being measured.3.1.5 burner, nflame device used to atomize the analyteby burning 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-m
17、ined for a specific element analysis.3.1.7 calibration curve, nplot of signal intensity versuselemental 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 or
18、ganization such as NIST, and whose properties areknown with sufficient accuracy to permit 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
19、 traceable certificate or otherdocumentation which is issued by a certifying body.3.1.10 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 me
20、asurement instrument or system.3.1.11 detection limit, nconcentration of an analyte thatresults 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 thealiqu
21、ot taken to the final diluted volume of its solution.3.1.12.1 DiscussionThe dilution factor 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 ho
22、llow cathode lamp, ndevice consisting of aquartz envelope containing a cathode of the metal 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 l
23、ine spectrum emitted by thehollow cathode lamp, excluding all other wavelengths.3.1.17 nebulizer, 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 and Tech-nology, Gaither
24、sburg, MD. Formerly known as National Bu-reau of Standards.3.1.19 precision, ncloseness of agreement 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 ser
25、vice the assurance that it meetsthe defined standards of quality with a stated level of confi-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
26、 in quality assur-ance program to determine and monitor the precision andstability of a measurement 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
27、should be properlystored to ensure sample integrity, and is available in sufficientquantity for 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 fo
28、rcalibration or quality control purposes in the laboratory.3.1.24 refractory elements, nelements 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 condition
29、s on identical test material would,in the long term and correct operation of the test method,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 identic
30、al test materials, would inthe long run, in the normal and correct operation of the testmethod, 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 t
31、he components of an emissionor absorption arranged in the order of some varying character-istics 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 tod
32、etermine the metal composition of various liquid matrices.Although usually AAS 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 s
33、ummarizes the protocols to be followed duringcalibration and verification of the instrument performance.D7740 1125. Significance and Use5.1 Accurate elemental analysis of petroleum products andlubricants is necessary for the determination of chemicalproperties, which are used to establish compliance
34、 with com-mercial and regulatory specifications.5.2 Atomic Absorption Spectrometry (AAS) 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 f
35、or such analysis. See Table 1.5.3 The advantage of using an AAS analysis include goodsensitivity for most metals, relative freedom from interfer-ences, and ability to calibrate the instrument based on elemen-tal standards irrespective of their elemental chemical forms.Thus, the technique has been a
36、method of choice in most of theoil industry laboratories. In many laboratories, AAS has beensuperseded by a superior ICP-AES technique (see PracticeD7260).5.4 Some of the ASTM AAS Standard Test Methods havealso been issued by other standard writing bodies as technicallyequivalent standards. See Tabl
37、e 2.6. Interferences6.1 Although over 70 elements can be determined by AASusually with a 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, m
38、atrix, emission,spectral, and background absorption interferences. Since theseinterferences 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 deco
39、mposed by the energy of the flame, a chemicalinterference exists. They can normally be overcome 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 o
40、f an electron from the atom,creating an ion, ionization interference can occur. They can 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
41、 either a sup-pression or enhancement of the analyte signal. Matrix interfer-ences occur 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
42、and stan-dard should be matched as closely as possible. Matrix inter-ferences can also be 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 Int
43、erferencesAt high analyte concentra-tions, the atomic absorption analysis for highly emissiveelements sometimes exhibits poor analytical precision, if theemission signal falls within the spectral bandpass being used.This interference can be compensated for by decreasing the slitwidth, increasing the
44、 lamp current, diluting the sample, and / orusing a cooler flame.6.1.5 Spectral InterferencesWhen 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. Aninte
45、rference by other atoms can occur when there is a sufficientoverlapping between radiation 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
46、inAAS. The interference can result in erroneously highresults. This can be overcome by using 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
47、 light from the lamp bymolecules in the flame. This interference cannot be correctedwith 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 t
48、he interferences in the AAS methods is to use atechnique called standard addition. IUPAC rule defines thistechnique as “Analyte Addition Method,” however, the phrase“standard addition method” is well known and is widely usedby the practitioners of AAS; hence, there is no need to adoptthe IUPAC rule.
49、 This technique takes longer time than thedirect analysis, but when only a few samples need to beanalyzed, or when the samples differ from each other in thematrix, or when the samples suffer from unidentified matrixTABLE 1 Applications of AAS for Metal Analysis 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, Calci
