Standard Test Method for Multielement Analysis of Crude Oils Using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

SIGNIFICANCE AND USE
Most often determined trace elements in crude oils are nickel and vanadium, which are usually the most abundant; however, as many as 45 elements in crude oils have been reported. Knowledge of trace elements in crude oil is important because they can have an adverse effect on petroleum refining and product quality. These effects can include catalyst poisoning in the refinery and excessive atmospheric emission in combustion of fuels. Trace element concentrations are also useful in correlating production from different wells and horizons in a field. Elements such as iron, arsenic, and lead are catalyst poisons. Vanadium compounds can cause refractory damage in furnaces, and sodium compounds have been found to cause superficial fusion on fire brick. Some organometallic compounds are volatile which can lead to the contamination of distillate fractions, and a reduction in their stability or malfunctions of equipment when they are combusted.
The value of crude oil can be determined, in part, by the concentrations of nickel, vanadium, and iron.
Inductively coupled plasma-atomic emission spectrometry (ICP-AES) is a widely used technique in the oil industry. Its advantages over traditional atomic absorption spectrometry (AAS) include greater sensitivity, freedom from molecular interferences, wide dynamic range, and multi-element capability. See Practice D7260.
SCOPE
1.1 This test method covers the determination of several elements (including iron, nickel, sulfur, and vanadium) occurring in crude oils.
1.2 For analysis of any element using wavelengths below 190 nm, a vacuum or inert gas optical path is required.
1.3 Analysis for elements such as arsenic, selenium, or sulfur in whole crude oil may be difficult by this test method due to the presence of their volatile compounds of these elements in crude oil; but this test method should work for resid 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 do not get aspirated in the nebulizer, low elemental values may result, particularly for iron and sodium. This can also occur if the elements are associated with water which can drop out of the solution when diluted with solvent.
1.4.1 An alternative in such cases is using Test Method D5708, Procedure B, which involves wet decomposition of the oil sample and measurement by ICP-AES for nickel, vanadium, and iron, or Test Method D5863, Procedure A, which also uses wet acid decomposition and determines vanadium, nickel, iron, and sodium using atomic absorption spectrometry.
1.4.2 From ASTM Interlaboratory Crosscheck Programs (ILCP) on crude oils data available so far, it is not clear that organic solvent dilution techniques would necessarily give lower results than those obtained using acid decomposition techniques.
1.4.3 It is also possible that, particularly in the case of silicon, low results may be obtained irrespective of whether organic dilution or acid decomposition is utilized. Silicones are present as oil field additives and can be lost in ashing. Silicates should be retained but unless hydrofluoric acid or alkali fusion is used for sample dissolution, they may not be accounted for.
1.5 This test method uses oil-soluble metals for calibration and does not purport to quantitatively determine insoluble particulates. Analytical results are particle size dependent and low results may be obtained for particles larger than a few micrometers.
1.6 The precision in Section 18 defines the concentration ranges covered in the interlaboratory study. However, lower and particularly higher concentrations can be determined by this test method. The low concentration limits are dependent on the sensitivity of the ICP instrument and the dilution factor used. The high concentration limits are determined by the product of the maximum concentration defined by the calibration curve and the sample dilution factor.
1.7 El...

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ASTM D7691-11 - Standard Test Method for Multielement Analysis of Crude Oils Using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7691 − 11
StandardTest Method for
Multielement Analysis of Crude Oils Using Inductively
1
Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
This standard is issued under the fixed designation D7691; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 This test method uses oil-soluble metals for calibration
and does not purport to quantitatively determine insoluble
1.1 This test method covers the determination of several
particulates. Analytical results are particle size dependent and
elements (including iron, nickel, sulfur, and vanadium) occur-
low results may be obtained for particles larger than a few
ring in crude oils.
micrometers.
1.2 For analysis of any element using wavelengths below
1.6 The precision in Section 18 defines the concentration
190 nm, a vacuum or inert gas optical path is required.
ranges covered in the interlaboratory study. However, lower
1.3 Analysis for elements such as arsenic, selenium, or
and particularly higher concentrations can be determined by
sulfur in whole crude oil may be difficult by this test method
thistestmethod.Thelowconcentrationlimitsaredependenton
due to the presence of their volatile compounds of these
the sensitivity of the ICP instrument and the dilution factor
elements in crude oil; but this test method should work for
used. The high concentration limits are determined by the
resid samples.
product of the maximum concentration defined by the calibra-
1.4 Because of the particulates present in crude oil samples,
tion curve and the sample dilution factor.
iftheydonotdissolveintheorganicsolventsusedoriftheydo
1.7 Elementspresentatconcentrationsabovetheupperlimit
not get aspirated in the nebulizer, low elemental values may
of the calibration curves can be determined with additional
result, particularly for iron and sodium. This can also occur if
appropriate dilutions and with no degradation of precision.
the elements are associated with water which can drop out of
1.8 As a generality based on this interlaboratory study (see
the solution when diluted with solvent.
18.1), the trace elements identifiable in crude oils can be
1.4.1 An alternative in such cases is using Test Method
divided into three categories:
D5708, Procedure B, which involves wet decomposition of the
oil sample and measurement by ICP-AES for nickel, 1.8.1 Element levels that are too low for valid detection by
ICP-AESandhence,cannotbedetermined:aluminum,barium,
vanadium, and iron, or Test Method D5863, Procedure A,
which also uses wet acid decomposition and determines lead, magnesium, manganese, and silicon.
vanadium, nickel, iron, and sodium using atomic absorption 1.8.2 Elements that are just at the detection levels of the
spectrometry.
ICP-AESmethodandhence,cannotbedeterminedwithagreat
1.4.2 From ASTM Interlaboratory Crosscheck Programs deal of confidence: boron, calcium, chromium, copper,
(ILCP) on crude oils data available so far, it is not clear that
molybdenum, phosphorus, potassium, sodium, and zinc. Per-
organic solvent dilution techniques would necessarily give haps the determination of these elements can be considered as
lower results than those obtained using acid decomposition
semi-quantitative.
techniques.
1.8.3 Elements that are at higher levels of concentration and
1.4.3 It is also possible that, particularly in the case of
canbedeterminedwithgoodprecision:iron,nickel,sulfur,and
silicon, low results may be obtained irrespective of whether
vanadium.
organicdilutionoraciddecompositionisutilized.Siliconesare
1.9 The detection limits for elements not determined by this
present as oil field additives and can be lost in ashing. Silicates
test method follow. This information should serve as an
should be retained but unless hydrofluoric acid or alkali fusion
indication as to what elements are not present above the
is used for sample dissolution, they may not be accounted for.
detection limits typically obtainable by ICP-AES instruments.
Element mg/kg
Aluminum 1
1
Barium 0.2
This test method is under the jurisdiction of ASTM Committee D02 on
Boron 1
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
Calcium 0.1
D02.03 on Elemental Analysis.
Chromium 0.1
Current edition approved Jan. 1, 2011. Published February 2011. DOI: 10.1520/
Copper 0.1
D7691–11.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7691 − 11
D6792 Practice for Quality System in Petroleum Products
Lead 1.4
Magnesium 1
and Lubricants Testin
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