ASTM D7303 Standard Test Method for Determination of Metals in Lubricating Greases by Inductively Coupled Plasma Atomic Emission Spectrometry
17. Report
17.1 Report mg/kg or mass % concentrations to three significant figures.
18. Precision and Bias
18.1 The precision of this test method was determined by statistical analysis of interlaboratory results. Ten participating laboratories analyzed nine grease samples in duplicate.
18.2 The precision of this test method was determined by statistical analyses of interlaboratory results collected in 2005. Ten participating laboratories analyzed nine samples of clay, lithium, and molybdenum, etc. greases in duplicate. Some laboratories used muffle furnace ashing, while others used high pressure microwave digestion systems. At the end all labs used ICP-AES for elemental measurements.
18.2.1 Many "less than" values were reported by some laboratories. Several elements had less than 30 degrees of freedom, and in some cases half the laboratories were biased high or low.
18.3 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.
18.4 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.
18.5 Bias - No bias could be calculated since no reference material for elemental content of grease is available.
19. Keywords
19.1 additive elements; aluminum; antimony; barium; calcium; emission spectrometry; grease; ICP; inductively-coupled plasma emission spectrometry; internal standard; iron; lithium; lubricating grease; magnesium; molybdenum; phosphorus; silicon; sodium; sulfur; zinc
