12. Report
12.1 Report the concentration of the individual aromatics or aromatics groups on an absolute basis to the nearest 0.1 liquid volume percent.
13. Precision and Bias
13.1 Precision - The precision of the test method as determined by a statistical examination of interlaboratory test results is as follows:
13.1.1 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 value only in one case in twenty:
13.1.2 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:
NOTE 6 - The precision was determined using conventional motor gasolines purchased on the open market and representative gasoline blending components. Benzene concentrations, in most of the samples, were less than 2 liquid volume percent. For more precise benzene analysis, at low concentration levels, Test Method D3606 should be used.
13.2 Bias - Since there is no accepted reference gasoline containing known concentrations of individual aromatics, the bias for the procedure in Test Method D4420 for measuring aromatics in finished gasoline can not be determined.
13.2.1 This test method uses purposely prepared calibration blends to establish the relationship between absolute detector response and known concentration for each of the individual aromatics or group of aromatics listed in the scope. The response factors so determined effectively compensate for any instrumental bias. The calibration blends used, however, are much simpler in composition than gasoline; thus matrix effects can not be adequately addressed and can be a source of bias.
14. Keywords
14.1 aromatics; benzene; gas chromatography; gasoline; toluene