ASTM D2789 Test Method for Hydrocarbon Types in Low Olefinic Gasoline by Mass Spectrometry
12. Calibration Data
12.1 Compositions of synthetic hydrocarbon mixtures are shown in Table 2. These mixtures were analyzed by cooperative programs and the results, as presented in Table 1, are the basis for the inverses in Table 3. Sensitivities and liquid volume factors which were applied to the calibration data in Table 1 are described in Table 4.
12.2 The inverses in Table 3 were calculated as follows:
12.2.1 For a given carbon number and for a specific hydrocarbon class the set of values ∑43/T, ∑41/T, etc., were divided by the largest number in the set. These new values and their hydrocarbon classes were listed in proper order to form an array or matrix.
12.2.2 All elements in this new array which were representative of one hydrocarbon class were multiplied by the corresponding pressure sensitivity for that class and carbon number.
12.2.3 The matrix as obtained in 12.2.2 was inverted.
12.2.4 The inverse terms for a given hydrocarbon class and carbon number were multiplied by the corresponding liquid volume factor. Finally, all new terms were divided by 100.
13. Precision and Bias
13.1 The precision of this test method as obtained by statistical examination of interlaboratory test results on samples having the composition given in Table 5 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 values shown in Table 5 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 values shown in Table 5 only in one case in twenty.
NOTE 10 - If samples are analyzed that differ appreciably in composition from those used for the interlaboratory study, this precision statement may not apply.
13.2 Bias - Bias cannot be determined because there is no acceptable reference material suitable for determining the bias for the procedure in this test.
14. Keywords
14.1 mass spectrometry; gasoline; hydrocarbon types; paraffins; monocycloparaffins; dicycloparaffins; alkylbenzenes; indans; naphthalenes
