ASTM D4739 for base number determination by potentiometric titration
13. Report
13.1 Report the results as base number, and strong base number, Test Method D4739.
14. Quality Control Checks
14.1 confirm the performance of the test procedure by analyzing a quality control (QC) sample that is, if possible, representative of the samples typically analyzed.
14.2 Prior to monitoring the measurement process, the user of the method needs to determine the average value and control limits of the QC sample.
14.3 Record the QC results and analyze by control charts or other statistically equivalent technique to ascertain the statistical control status of the total testing process. Any out of control data should trigger investigation for root cause(s). The results of this investigation may, but not necessarily, result in instrument recalibration.
14.4 The frequency of QC testing is dependent on the criticality of the quality being measured, the demonstrated stability of the testing process, and customer requirement. Generally, a QC sample should be analyzed each testing day. The QC frequency should be increased if a large number of samples are routinely analyzed. However, when it is demonstrated that the testing is under statistical control, the QC testing frequency may be reduced.
15. Precision and Bias
15.1 Precision - The precision of this test method as determined by statistical examination of results on nine samples of new and used oils run in duplicate by twelve different laboratories is as follows:
15.1.1 Base Number:
15.1.1.1 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 following value only in one case in twenty:
10.4 % of the mean of the two test results
15.1.1.2 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 value only in one case in twenty:
21.1 % of the mean of the two test results
NOTE 13 - The range of base number values for which the precision values were established was 0.5 to 70.
15.1.2 Strong Base Number - Precision data have not been developed for strong base number because of its rare occurrence.
15.2 Bias - A statement of bias is not applicable since a standard reference material for this property is not available.
16. Keywords
16.1 base number; lubricants; petroleum products; potentiometric titration
