ASTM D3525 Standard Test Method for Gasoline Diluent in Used Gasoline Engine Oils by Gas Chromatography
10. Calculation
10.1 Record the cumulative area under the chromatogram from time zero to the start of the n-tetradecane peak. Record the area under the n-tetradecane peak.
10.2 Calculate the weight percent (mass percent) of fuel dilution in the sample as follows:
where:
F = fuel dilution, mass %,
A1 = area counts under the chromatogram before the n-tetradecane peak,
A2 = area counts under the n-tetradecane peak on the chromatogram,
W1 = mass of n-tetradecane used in 8.1, and
X1 = mass of sample used in 8.1.
NOTE 9 - The conditions specified have not shown evidence of additive or base oil decomposition. Appearance of abnormal peaks on the chromatograph may indicate such decomposition. In this event it would be desirable to obtain a chromatogram on the unused oil if available and to make a correction to the indicated fuel dilution.
11. Precision and Bias
11.1 The following criteria should be used for judging the acceptability of results (95 % probability):
11.1.1 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:
0.28 mass %
11.1.2 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 out of twenty:
1.64 mass %
NOTE 10 - This precision was developed using single-flame ionization detectors and column temperature programming. The stated precision does not apply to other chromatographic systems.
11.2 Bias - No estimate of the bias of this test method is possible because of the empirical nature of this test method.
12. Keywords
12.1 gasoline; lubricating oil; fuel dilution; gas chromatography