ASTM D6277 Method for Determination of Benzene in Spark-Ignition Engine Fuels
ASTM D6277 Standard Test Method for Determination of Benzene in Spark-Ignition Engine Fuels Using Mid Infrared Spectroscopy
14. Report
14.1 Report the following information:
14.1.1 Filter instruments (Test Method D6277a).
14.1.1.1 Volume % benzene by Test Method D6277a, to the nearest 0.01%.
14.1.2 FTIR instruments with PLS calibration (Test Method D6277b).
14.1.2.1 Volume % benzene by Test Method D6277b, to the nearest 0.01%.
14.1.3 FTIR instruments with CLS calibration (Test Method D6277c).
14.1.3.1 Volume % benzene by Test Method D6277c, to the nearest 0.1%.
15. Precision and Bias
15.1 Interlaboratory tests of each of the procedures (filter instruments, FTIR instruments with PLS calibration, and FTIR instruments with CLS calibration) were carried out using twenty samples that covered the range from 0 to 1.8 volume % and at least six laboratories for each of the procedures. An additional sample containing approximately 4 volume % benzene was also included in the interlaboratory results. The precision of the test method as obtained by statistical examination of interlaboratory results is summarized in Table 2 and Table 3 and is as follows:
15.2 Repeatability for Filter Based Mid IR Instruments - For benzene concentrations between 0.1 and 1.8 volume %, the difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
r = 0.021 + 0.027 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between successive test results, obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.18 only in one case in twenty.
15.3 Repeatability for FTIR Instruments Using PLS Calibration Instruments - For benzene concentrations between 0.1 and 1.8 volume %, the difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
r = 0.013 + 0.052 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.14 only in one case in twenty.
15.4 Repeatability for FTIR Instruments Using a Classical Least Squares Calibration - For benzene concentrations between 0.1 and 1.8 volume %, the difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
r = 0.047 + 0.043 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.18 only in one case in twenty.
15.5 Reproducibility for Filter Based Mid IR Instruments - For benzene concentrations between 0.1 and 1.8 volume %, the difference between two single and independent results, obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
R = 0.121 + 0.012 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between two single and independent results, obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.59 only in one case in twenty.
15.6 Reproducibility for FTIR Instruments Using a PLS Calibration Instrument - For benzene concentrations between 0.1 and 1.8 volume %, the difference between two single and independent results obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
R = 0.022 + 0.118 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between two single and independent results obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.47 only in one case in twenty.
15.7 Reproducibility for FTIR Instruments Using a Classical Least Squares Calibration Instrument - For benzene concentrations between 0.1 to 1.8 volume %, the difference between two single and independent results obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed the following values only in one case in twenty.
R = 0.099 + 0.031 X
where X is the benzene concentration determined. For the one sample at approximately 4 volume % benzene, the difference between two single and independent results obtained by different operators working in different laboratories on identical test samples would, in the long run, and in the normal and correct operation of the test method, exceed 0.23 only in one case in twenty.
15.8 Bias - Since there were no suitable reference materials included in the interlaboratory test program, no statement of bias is being made. However, the samples of the test program were shared with an interlaboratory study of Test Method D5769 and small biases (see Note 2) relative to that test method were observed. The relative biases were not the same for all procedures, nor were they the same for all samples within each procedure. Because such sample biases are not correctable, users wishing to use this test method to substitute for Test Method D5769, or conversely, are cautioned to consider the specific source or sources of subject fuels and to ensure, through periodic comparative testing, that any differences are consistent and manageable.
NOTE 2 - The average bias, relative to Test Method D5769, was -0.06 volume % for the FTIR procedures and +0.06 for the filter procedure. After accounting for the averages, the fuel-specific differences exceeded 0.1 volume % for only one fuel on one procedure (out of 62 combinations).
16. Keywords
16.1 aromatics; benzene; infrared spectroscopy; spark-ignition engine fuel
