ASTM D 7691 : 2023 : REDLINE
Current
The latest, up-to-date edition.
Standard Test Method for Multielement Analysis of Crude Oils Using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
English
07-06-2023
Important note : Users cannot be edited or removed once added to your Multi user PDF.| Committee |
D 02
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| DocumentType |
Redline
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| Pages |
20
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| PublisherName |
American Society for Testing and Materials
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| Status |
Current
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| Supersedes |
1.1This test method covers the determination of several elements (including iron, nickel, sulfur, and vanadium) occurring in crude oils.
1.2For analysis of any element using wavelengths below 190 nm, a vacuum or inert gas optical path is required.
1.3Analysis 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.
1.4Because 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.
1.4.1An 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.
1.4.2From 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.2
1.4.3It 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.
1.5This 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.
1.6The 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.
1.7Elements present at concentrations above the upper limit of the calibration curves can be determined with additional appropriate dilutions and with no degradation of precision.
1.8As a generality based on this interlaboratory study (see 18.1), the trace elements identifiable in crude oils can be divided into three categories:
1.8.1Element levels that are too low for valid detection by ICP-AES and hence, cannot be determined: aluminum, barium, lead, magnesium, manganese, and silicon.
1.8.2Elements that are just at the detection levels of the ICP-AES method and hence, cannot be determined with a great deal of confidence: boron, calcium, chromium, copper, molybdenum, phosphorus, potassium, sodium, and zinc. Perhaps the determination of these elements can be considered as semi-quantitative.
1.8.3Elements that are at higher levels of concentration and can be determined with good precision: iron, nickel, sulfur, and vanadium.
1.9The detection limits for elements not determined by this test method follow. This information should serve as an indication as to what elements are not present above the detection limits typically obtainable by ICP-AES instruments.
| Element | mg/kg |
| Aluminum | 1 |
| Barium | 0.2 |
| Boron | 1 |
| Calcium | 0.1 |
| Chromium | 0.1 |
| Copper | 0.1 |
| Lead | 1.4 |
| Magnesium | 1 |
| Manganese | 0.1 |
| Molybdenum | 0.2 |
| Phosphorous | 1 |
| Potassium | 0.5 |
| Silicon | 4 |
| Zinc | 0.5 |
1.10This test method determines all possible elements simultaneously and is a simpler alternative to Test Methods D5184, D5708, or D5863.
1.11The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.12This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.13This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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