ASTM_D_7691_-_11e1.pdf

Designation:D7691111Standard 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 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 covers 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 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 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 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 Crosscheck 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 irrespective 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 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 covered 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 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 this 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 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 that 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 limits 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 2011.DOI:10.1520/D769111E01.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 Elementmg/kgAluminum1Barium0.2Boron1Calcium0.1Chromium0.1Copper0.1Lead1.4Magnesium1Manganese0.1Molybdenum0.2Phosphorous1Potassium0.5Silicon4Zinc0.51.10 This test method determines all possible elementssimultaneously and is a simpler alternative to Test MethodsD5184,D5708,or D5863.1.11 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