13. Report
13.1 Report the sulfate content results to the nearest 0.01 mg/kg over the 1.0 - 20 mg/kg range.
14. Quality Control (QC)
14.1 Confirm the performance of the instrument or the test procedure by analyzing one or more quality check sample(s) after each calibration and on at least each day of use thereafter. For example, a good check sample could be a single representative ethanol sample (see X1.5) that is analyzed repetitively. These results are plotted in control charts to check the system for statistical stability, as in X1.3.
14.1.1 When QC/Quality Assurance (QA) protocols are already established in the testing facility, they can be used when they confirm the reliability of the test result.
14.1.2 When there is no QC/QA protocol established in the testing facility, Appendix X1 can be used to define a suitable QC/QA system.
15. Precision and Bias
15.1 Precision - The precision of this test method as determined by the statistical evaluation of the 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 material would, in the long run, in the normal and correct operation of the test method exceed the following values only in one case in twenty.
15.1.1.1 Existent Inorganic Sulfate - The pooled limit of quantitation (PLOQ) is 1.0 mg/kg. Repeatability r between 1.0 and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
where:
X = analyte concentration, mg/kg.
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, in the normal and correct operation of the test method exceed the following values only in one case in twenty.
15.1.2.1 Existent Inorganic Sulfate - Reproducibility R between 1.0 and 20 mg/kg existent inorganic sulfate measured is calculated as follows:
where:
X = analyte concentration, mg/kg.
15.2 Bias - Since there was no generally accepted reference material available at the time of the interlaboratory testing, no statement of bias can be made at this time.
15.3 Table 2 shows precision values calculated from Eq 7 and Eq 8.
16. Keywords
16.1 ethanol; existent inorganic sulfate; lead; potentiometric; sulfate; titration