ASTM D7040 Standard Test Method for Determination of Low Levels of Phosphorus in ILSAC GF 4 and Similar Grade Engine Oils by Inductively Coupled Plasma Atomic Emission Spectrometry
15. Calculation and Report
15.1 Calculate concentrations, based on sample, using Eq 1. Generally, the ICP software performs this calculation automatically.
C = S x [W1 + W2 + W3]/W1
where:
C = analyte concentration in the sample, mg/kg,
S = analyte concentration in the test specimen, mg/kg (refer to Section 13),
W1 = sample mass, g,
W2 = diluent mass, g, and
W3 = base oil mass (if any), g.
15.2 For each analyte, report mg/kg to three significant figures.
16. Precision and Bias
16.1 Precision - The precision of this test method was determined by statistical analysis of interlaboratory results. Ten participating laboratories analyzed nine samples in duplicate. In this study, dilution solvents were limited to mixed xylenes, o-xylene, and kerosine. All laboratories used a peristaltic pump, and internal standard and background correction. The phosphorus content ofthe samples used in this study was in the concentration range 500 mg/kg to 800 mg/kg.
16.1.1 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 1 only in one case in twenty. (Also, see Table 2.)
16.1.2 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 1 only in one case in twenty. (Also, see Table 2.)
16.2 Bias - Since there are no NIST standard reference materials of GF 4 type oils with certified phosphorus content available, the bias of the test method could not be determined.
17. Keywords
17.1 additive-elements; emission-spectrometry; GF 4 oils; ICP-AES; inductively-coupled plasma atomic emission spectrometry; internal standard; lubricating oils; phosphorus
