ASTM D6443 Copper, Phosphorus and Sulfur in Unused Lubricating Oils and Additives
ASTM D6443 Standard Test Method for Determination of Calcium, Chlorine, Copper, Magnesium, Phosphorus, Sulfur, and Zinc in Unused Lubricating Oils and Additives by Wavelength Dispersive X-ray Fluorescence Spectrometry (Mathematical Correction Procedure)
13. Reporting
13.1 For samples that required dilution, multiply results by the dilution factor.
13.2 Report results in mass %, using three significant figures for concentrations greater than 0.0100 %, two significant figures for concentrations between 0.0010 % and 0.0100 %, and one significant figure for concentrations below 0.0010 %.
13.3 For guidance in rounding significant figures, refer to Practice E 29.
13.4 Report results that are below the limit of detection as not detected or less than, followed by the LOD value. The value assigned to LOD can be the appropriate value listed in Table 2, or a value, characteristic of an individual laboratory's performance, determined with the same methodology used in Table 2, or some plausible value mutually accepted by interested participants.
13.4.1 For samples that require dilution, the appropriate limit of detection is the limit of detection determined for the diluted specimen multiplied by the sample dilution factor.
14. Precision and Bias
14.1 The precision of this test method was determined by statistical analysis of interlaboratory results. In this study, nine laboratories analyzed eleven oils and three additives in duplicate. To estimate bias, two of the oils were lab synthesized using Conostan11 standards. Six labs used theoretical alphas exclusively, two labs used a combination of theoretical and empirical, and one lab used empirical alphas exclusively. A variety of oil soluble standards was used by the laboratories participating in the interlaboratory study. The ranges of analyte concentrations together with their precisions are listed below.
14.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operation conditions on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values in Tables 4-7 in only one case in twenty.
14.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the values in Tables 4-7 in only one case in twenty.
14.2 Bias - An indication of bias was determined from interlaboratory study results obtained on two different laboratory synthesized oils. One lab blend (Oil G) was prepared by combining Conostan 5000 ppm standards (Ca, Zn, Cu, P), Conostan concentrate (Mg), 2-chloro-paraxylene, base oil, and mineral oil. The following concentrations were considered known: Ca, 0.0024 %; Zn, 0.0023 %; Cu, 0.0023 %; P, 0.0026 %; Mg, 0.0103 %; Cl, 0.0035 %. Similarly, a second lab blend (Oil J) was prepared by combining Conostan concentrates (Zn, P, Ca, Mg), Conostan 5000 ppm (Cu), 2-chloro-paraxylene, and mineral oil. The following concentrations were considered known: Ca, 0.1303 %; P, 0.1487 %; Zn, 0.1362 %; Mg, 0.1103 %; Cu, 0.0143 %; Cl, 0.0275 %. For these two blends, Table 8 summarizes interlaboratory results as they pertain to bias.
14.2.1 Sulfur was not included in the bias estimation because some of the components used to blend the oils contained sulfur at uncertified concentrations.
14.2.2 Chlorine was not included in the bias estimation because contamination was suspected.
14.3 Limit of Detection and Limit of Quantification - The LOD and LOQ determined from data from the interlaboratory study on precision are listed in Table 2. The LOD is herein defined as three times Sr, and the LOQ is herein defined as ten times Sr, where Sr is the pooled repeatability standard deviation determined at concentration(s) less than approximately five times the estimated limit of detection (see also 40 CFR 136 Appendix B).
14.3.1 LOD and LOQ values for sulfur were not estimated because the sulfur concentrations in the interlaboratory study samples were too high.
15. Keywords
15.1 additive elements; additives; calcium; chlorine; copper; lubricating oils; magnesium; phosphorus; sulfur; wavelength dispersive X-ray spectrometry; zinc
