ASTM D7751 Standard Test Method for Determination of Additive Elements in Lubricating Oils by EDXRF Analysis
15. Report
15.1 For all samples analyzed, calculate and report the result in accordance with Section 14. Report the result as the total concentration in mass % to three significant figures (x.xx, 0.xxx) at levels greater than 0.1 %, to two significant figures (0.0xx) at levels greater than 0.01 %, and to one significant figure (0.00x) at levels equal or lower than 0.01 %. State that the results were obtained according to Test Method D7751.
16. Precision and Bias
16.1 Precision - The precision of this test method was determined by statistical analysis of the interlaboratory study (ILS) results. The ILS was conducted in 2016, and included 21 laboratories analyzing 16 samples (blended lubricating oils) in duplicates. The participating laboratories used a combination of FP and other matrix and interelements effects corrections. A variety of calibration standards was used. The statistical analysis showed good repeatability (r) and good reproducibility (R).
16.1.1 Repeatability - The difference between successive 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 following values in Table 4 and Table 5 in only one case in twenty.
16.1.2 Reproducibility - The difference between successive test results obtained by different operators with different 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 following values in Table 6 and Table 7 in only one case in twenty.
16.1.3 Bias - No information can be presented on the bias of the procedure in Test Method D7751 for measuring magnesium, phosphorus, sulfur, chlorine, calcium, zinc, and molybdenum, because no material having an accepted reference value was available in the interlaboratory study.
17. Keywords
17.1 additive elements; additives; calcium; chlorine; EDXRF; energy dispersive; lubricating oil; magnesium; molybdenum; phosphorus; spectrometry; sulfur; X-ray; XRF; zinc
