1、Designation: D7691 111Standard Test Method forMultielement Analysis of Crude Oils Using InductivelyCoupled Plasma Atomic Emission Spectrometry (ICP-AES)1This standard is issued under the fixed designation D7691; the number immediately following the designation indicates the year oforiginal adoption
2、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.1NOTEAppendix X2 was editorially corrected in August 2014.1. Scope1.1 This test method co
3、vers the determination of severalelements (including iron, nickel, sulfur, and vanadium) occur-ring in crude oils.1.2 For analysis of any element using wavelengths below190 nm, a vacuum or inert gas optical path is required.1.3 Analysis for elements such as arsenic, selenium, orsulfur in whole crude
4、 oil may be difficult by this test methoddue to the presence of their volatile compounds of theseelements in crude oil; but this test method should work forresid samples.1.4 Because of the particulates present in crude oil samples,if they do not dissolve in the organic solvents used or if they donot
5、 get aspirated in the nebulizer, low elemental values mayresult, particularly for iron and sodium. This can also occur ifthe elements are associated with water which can drop out ofthe solution when diluted with solvent.1.4.1 An alternative in such cases is using Test MethodD5708, Procedure B, which
6、 involves wet decomposition of theoil sample and measurement by ICP-AES for nickel,vanadium, and iron, or Test Method D5863, Procedure A,which also uses wet acid decomposition and determinesvanadium, nickel, iron, and sodium using atomic absorptionspectrometry.1.4.2 From ASTM Interlaboratory Crossch
7、eck Programs(ILCP) on crude oils data available so far, it is not clear thatorganic solvent dilution techniques would necessarily givelower results than those obtained using acid decompositiontechniques.1.4.3 It is also possible that, particularly in the case ofsilicon, low results may be obtained i
8、rrespective of whetherorganic dilution or acid decomposition is utilized. Silicones arepresent as oil field additives and can be lost in ashing. Silicatesshould be retained but unless hydrofluoric acid or alkali fusionis used for sample dissolution, they may not be accounted for.1.5 This test method
9、 uses oil-soluble metals for calibrationand does not purport to quantitatively determine insolubleparticulates. Analytical results are particle size dependent andlow results may be obtained for particles larger than a fewmicrometers.1.6 The precision in Section 18 defines the concentrationranges cov
10、ered in the interlaboratory study. However, lowerand particularly higher concentrations can be determined bythis test method. The low concentration limits are dependent onthe sensitivity of the ICP instrument and the dilution factorused. The high concentration limits are determined by theproduct of
11、the maximum concentration defined by the calibra-tion curve and the sample dilution factor.1.7 Elements present at concentrations above the upper limitof the calibration curves can be determined with additionalappropriate dilutions and with no degradation of precision.1.8 As a generality based on th
12、is interlaboratory study (see18.1), the trace elements identifiable in crude oils can bedivided into three categories:1.8.1 Element levels that are too low for valid detection byICP-AES and hence, cannot be determined: aluminum, barium,lead, magnesium, manganese, and silicon.1.8.2 Elements that are
13、just at the detection levels of theICP-AES method and hence, cannot be determined with a greatdeal of confidence: boron, calcium, chromium, copper,molybdenum, phosphorus, potassium, sodium, and zinc. Per-haps the determination of these elements can be considered assemi-quantitative.1.8.3 Elements th
14、at are at higher levels of concentration andcan be determined with good precision: iron, nickel, sulfur, andvanadium.1.9 The detection limits for elements not determined by thistest method follow. This information should serve as anindication as to what elements are not present above thedetection li
15、mits typically obtainable by ICP-AES instruments.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.03 on Elemental Analysis.Current edition approved Jan. 1, 2011. Published February
16、 2011. DOI: 10.1520/D769111E01.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Element mg/kgAluminum 1Barium 0.2Boron 1Calcium 0.1Chromium 0.1Copper 0.1Lead 1.4Magnesium 1Manganese 0.1Molybdenum 0.2Phosphorous 1Potassium 0.5Silicon 4Z
17、inc 0.51.10 This test method determines all possible elementssimultaneously and is a simpler alternative to Test MethodsD5184, D5708,orD5863.1.11 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.12 This standard does not purpor
18、t 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.2. Referenced Documents2.1 ASTM Standards:2C1109
19、 Practice for Analysis of Aqueous Leachates fromNuclear Waste Materials Using Inductively CoupledPlasma-Atomic Emission SpectroscopyD1552 Test Method for Sulfur in Petroleum Products (High-Temperature Method)D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Auto
20、matic Sampling of Petroleum andPetroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use asAnalytical StandardsD5184 Test Methods for Determination of Aluminum andSilicon in Fuel Oils by Ashing, Fusion, InductivelyCoupled Plasma Atomic Emission Spectrometry, andAtomic Absorption Spec
21、trometryD5185 Test Method for Multielement Determination ofUsed and Unused Lubricating Oils and Base Oils byInductively Coupled Plasma Atomic Emission Spectrom-etry (ICP-AES)D5708 Test Methods for Determination of Nickel,Vanadium, and Iron in Crude Oils and Residual Fuels byInductively Coupled Plasm
22、a (ICP) Atomic EmissionSpectrometryD5854 Practice for Mixing and Handling of Liquid Samplesof Petroleum and Petroleum ProductsD5863 Test Methods for Determination of Nickel,Vanadium, Iron, and Sodium in Crude Oils and ResidualFuels by Flame Atomic Absorption SpectrometryD6299 Practice for Applying S
23、tatistical 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 of Inductively Coupled Plasma-Atomic
24、 EmissionSpectrometry (ICP-AES) for Elemental Analysis of Petro-leum Products and LubricantsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related Materials3. Terminology3.1 For the definition of emission spectroscopy, refer toTerminology E135.3.2 Definitions of Terms Specifi
25、c to This Standard:3.2.1 analyte, nelement whose concentration is beingdetermined.3.2.2 Babington-type nebulizer, ndevice that generates anaerosol by flowing a liquid over a surface that contains anorifice from which gas flows at a high velocity.3.2.3 calibration, nprocess by which the relationshipb
26、etween signal intensity and elemental concentration is deter-mined for a specific element analysis.3.2.4 calibration curve, nplot of signal intensity versuselemental concentration using data obtained by making mea-surements with standards.3.2.5 detection limit, nconcentration of an analyte thatresul
27、ts in a signal intensity that is some multiple (typically two)times the standard deviation of the background intensity at themeasurement wavelength.3.2.6 inductively-coupled plasma (ICP), nhigh-temperature discharge generated by flowing an ionizable gasthrough a magnetic field induced by a load coil
28、 that surroundsthe tubes carrying the gas.3.2.7 linear response range, nelemental concentrationrange over which the calibration curve is a straight line, withinthe precision of the test method.3.2.8 profiling, ntechnique that determines the wave-length for which the signal intensity measured for a p
29、articularanalyte is a maximum.3.2.9 radio frequency (RF), nrange of frequencies be-tween the audio and infrared ranges (3 to 300 GHz).4. Summary of Test Method4.1 This test method usually requires several minutes persample.Aweighed portion of a thoroughly homogenized crudeoil is diluted tenfold by w
30、eight with mixed xylenes, kerosene,or other suitable solvent. Standards are prepared in the samemanner.Amandatory internal standard is added to the solutionsto compensate for variations in test specimen introductionefficiency. The solutions are introduced to the ICP instrumentby a peristaltic pump.
31、By comparing emission intensities of2For 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.D7691 1112elements in the
32、 test specimen with emission intensities mea-sured with the standards, the concentrations of elements in thetest specimen are calculable.5. Significance and Use5.1 Most often determined trace elements in crude oils arenickel and vanadium, which are usually the most abundant;however, as many as 45 el
33、ements in crude oils have beenreported. Knowledge of trace elements in crude oil is importantbecause they can have an adverse effect on petroleum refiningand product quality. These effects can include catalyst poison-ing in the refinery and excessive atmospheric emission incombustion of fuels. Trace
34、 element concentrations are alsouseful in correlating production from different wells andhorizons in a field. Elements such as iron, arsenic, and lead arecatalyst poisons. Vanadium compounds can cause refractorydamage in furnaces, and sodium compounds have been foundto cause superficial fusion on fi
35、re brick. Some organometalliccompounds are volatile which can lead to the contamination ofdistillate fractions, and a reduction in their stability or mal-functions of equipment when they are combusted.5.2 The value of crude oil can be determined, in part, by theconcentrations of nickel, vanadium, an
36、d iron.5.3 Inductively coupled plasma-atomic emission spectrom-etry (ICP-AES) is a widely used technique in the oil industry.Its advantages over traditional atomic absorption spectrometry(AAS) include greater sensitivity, freedom from molecularinterferences, wide dynamic range, and multi-element cap
37、abil-ity. See Practice D7260.6. Interferences6.1 SpectralThere are no known spectral interferencesbetween elements covered by this test method when using thespectral lines listed in Table 1. However, if spectral interfer-ences exist because of other interfering elements or selection ofother spectral
38、 lines, correct for the interference using thetechnique described in Test Method D5185.6.2 Check all spectral interferences expected from theelements listed in Table 1. Follow the manufacturers operatingguide to develop and apply correction factors to compensatefor the interferences. To apply interf
39、erence corrections, allconcentrations shall be within the previously established linearresponse range of each element listed in Table 1.(WarningCorrect profiling is important to reveal spectral interferencesfrom high concentrations of some elements on the spectrallines used for determining trace met
40、als.)6.2.1 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 supplied by theinstrument manufacturer or the empirical method describedbelow. Deta
41、ils of the empirical method are given in TestMethod C1109 and by Boumans.3This empirical correctionmethod cannot be used with scanning spectrometer systemswhen both the analytical and interfering lines cannot be locatedprecisely and reproducibly. With any instrument, the analystshall always be alert
42、 to the possible presence of unexpectedelements producing interfering spectral lines.6.2.2 The empirical method of spectral interference correc-tion uses interference correction factors. These factors aredetermined by analyzing the single-element, high purity solu-tions under conditions matching as
43、closely as possible thoseused for test specimen analysis. Unless plasma conditions canbe accurately reproduced from day to day, or for longerperiods, interference correction factors found to affect theresults significantly shall be redetermined each time specimensare analyzed.6.2.3 Interference corr
44、ection factors can be negative ifoff-peak background correction is employed for element, i.Anegative Kia correction factor can result when an interferingline is encountered at the background correction wavelengthrather than at the peak wavelength.6.3 Viscosity EffectsDifferences in the viscosities o
45、f testspecimen solutions and standard solutions can cause differ-ences in the uptake rates. These differences can adversely affectthe accuracy of the analysis. The effects can be reduced byusing a peristaltic pump to deliver solutions to the nebulizer orby the use of internal standardization, or bot
46、h. When severeviscosity effects are encountered, dilute the test specimen andstandard twentyfold rather than tenfold while maintaining thesame concentration of the internal standard. See Table 2.3Boumans, P. W. J. M., “Corrections for Spectral Interferences in OpticalEmission Spectrometry with Speci
47、al Reference to the RF Inductively CoupledPlasma,” Spectrochimica Acta, Vol 31B, 1976, pp. 147-152.TABLE 1 Elements Determined and Suggested WavelengthsAElement Wavelength, nmAluminum 308.215, 396.153, 309.271, 237.01Barium 233.53, 455.403, 493.410Boron 249.773, 182.59, 249.68Calcium 315.887, 317.93
48、3, 364.44, 422.67Chromium 205.552, 267.716, 298.92, 283.563Copper 324.754, 219.226Iron 259.94, 238.204, 271.44, 259.837Lead 220.353, 224.688, 283.306Magnesium 279.079, 279.553, 285.21, 293.65Manganese 257.61, 293.31, 293.93, 294.92Molybdenum 202.03, 281.616, 204.598, 203.844Nickel 231.604, 227.02, 2
49、21.648, 341.476Phosphorus 177.51, 178.289, 214.914, 253.40Potassium 766.491, 769.896Sodium 588.995, 330.29, 589.3, 589.592Silicon 288.159, 251.611, 212.412, 282.851Sulfur 180.731, 182.04, 182.62Vanadium 292.403, 309.31, 310.23, 311.07Zinc 202.551, 206.209, 213.856, 334.58, 481.05, 202.48AThese wavelengths are only suggested and do not represent all possiblechoices. Not all of these elements were determined in this interlaboratory study.TABLE 2 Suggested Internal StandardsElement Concentration, mg/kg Wavelength,ANmCadmium 10 226.502; 228.802; 214.438Cobalt 10 228.616;
