11. Report
11.1 Report the mole percent aromatic hydrogen atoms or the mole percent aromatic carbon atoms to one decimal place.
12. Precision and Bias
12.1 The precision of this test method is dependent on the aromatic content of the sample.
12.2 Precision - The precision of this test method as determined by the statistical examination of interlaboratory test results in the range 1 to 78 (aromatic hydrogen content) and 8 to 93 (aromatic carbon content) is as follows:
12.2.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions or identical test material would, in the long run, in the normal and correct operation of this test method, exceed the following values only in one case in twenty:
Where X is the aromatic content determined from the NMR measurement.
12.2.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test materials would, in the long run, exceed the following values only in one case in twenty:
Where X is the aromatic content determined from the NMR measurement.
NOTE 2 - Precision limits are based on a round-robin test program carried out in 1985 and 1986 by the Institute of Petroleum (see IP Method BD) and ASTM Committee D02.04. Twelve cooperator laboratories tested five oils, namely a lubricating oil, a gas oil, two aromatic distillates, and an anthracene oil, whose aromatic hydrogen and carbon contents varied as described in 12.2.
12.2.3 Bias - For pure hydrocarbons consisting of a single compound or a known mixture of known aromatic compounds where the aromatic hydrogen or carbon content is either known from the compound molecular structure or can be calculated from the known concentrations of different molecular structures, no bias of the NMR method with respect to the known or calculated value is observed. Since there is no accepted reference method suitable for measuring bias on a hydrocarbon oil composed of an unknown mixture of many aromatic compounds, the bias cannot be determined on such materials.
13. Keywords
13.1 aromatic carbon content; aromatic hydrogen content; continuous wave; Fourier transform; hydrocarbon oils; NMR; nuclear magnetic resonance spectroscopy