ASTM D7691 Standard Test Method for Multielement Analysis of Crude Oils Using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)
17. Report
17.1 Report mg/kg to two to three significant figures for the elements determined by this test method. State that these analyses were done by Test Method D7691.
18. Precision and Bias
18.1 Precision - The precision of this test method was determined by statistical analysis of interlaboratory results. In this study, dilution solvents were limited to xylene or kerosine. All laboratories used Babington-type nebulizers, peristaltic pumps, and background correction, and internal standards. Eleven laboratories analyzed 18 specimens in duplicate. The samples included 12 diverse crude oils, three NIST SRMs, and three ASTM ILCP crude oil samples.
18.1.1 Repeatability - The difference between two test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 3 only in one case in twenty.
18.1.2 Reproducibility - The difference between two single and independent results, obtained by different operators working in different laboratories on identical test materials, would in the long run, in the normal and correct operation of the test method, exceed the values in Table 3 only in one case in twenty.
18.1.3 Precisions for some typical concentrations of these elements calculated from the precisions given in Table 3 are given in Table 4.
18.2 Bias - Bias was evaluated by analyzing quantitative dilutions of NIST SRM 2721 and 2722 and RM 8505. The means of the reported values for sulfur and vanadium do not differ from the corresponding expected values by more than the repeatability of the method, when no significant interferences from other elements exist (see 6.1).
19. Keywords
19.1 crude oil; inductively coupled plasma-atomic emission spectrometry; iron; nickel; sulfur; vanadium
