ASTM D6445 Standard Test Method for Sulfur in Gasoline by Energy-Dispersive X-ray Fluorescence Spectrometry
13. Report
13.1 Report the result as the total sulfur content to the nearest 1 mg/kg, and state that the results were obtained in accordance with Test Method D6445.
14. Quality Control
14.1 For the purpose of establishing the in statistical control status of the testing process since the last valid calibration, QC standards prepared from material(s) selected and stored according to 10.3 and 10.4 are regularly tested as if they were production samples. Results are recorded and analyzed by control charts (see Note 6) or other statistically equivalent techniques to ascertain the statistical control status of the total testing process. An investigation for root cause(s) shall be conducted when there are out of control data. The outcome of this investigation may, but not necessarily, result in instrument recalibration. In absence of other explicit requirements, the frequency of QC standards testing is dependent on the criticality of the quality being measured and the demonstrated stability of the testing process. It is recommended that at least one type of QC standard that is regularly tested be representative of samples routinely analyzed.
NOTE 6 - The precise method of control charting, chart interpretation, and corrective action is left to the individual laboratory since the topic is outside the scope of this test method. One resource, however, that may be useful is MNL #7.
15. Precision and Bias
15.1 Precision - The precision of this test method as obtained by statistical analysis of interlaboratory test results is as follows:
15.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the following values in only one case in twenty:
where:
X is the sulfur concentration in mg/kg.
Repeatability values for some typical sulfur concentrations are shown in Table 4.
15.1.2 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, exceed the following values in only one case in twenty:
where:
X is the sulfur concentration in mg/kg.
Reproducibility values for some typical sulfur concentrations are shown in Table 4.
15.2 Bias - Since no accepted reference materials were used in the interlaboratory test, no statement on bias is being made.
16. Keywords
16.1 analysis; energy dispersive; petroleum; spectrometry; sulfur; X ray