The HC22 method, first published in 1967, is a high-resolution adaptation of the original mass-spectrometric methods for analyzing petroleum distillates.1,2 Eighteen saturate and aromatic hydrocarbon types and four aromatic types containing sulfur are determined. It is applicable to olefin-free petroleum distillates boiling in a range from 250 °F to 1050 °F (121 °C to 566 °C), with average carbon numbers between 12 and 36, and having less than 5 mol% total of compounds containing oxygen, nitrogen, and sulfur. Unlike the ASTM methods, HC22 does not require separation of the distillate into saturates and aromatics prior to the analysis. Auxiliary information, such as simulated distillation data (ASTM D 2887), is used to select the proper matrices required for the calculations.
Quantitative results are presented in liquid-volume percent and in weight percent. In addition, the method provides weight percents of carbon, hydrogen, and thiophenic sulfur, the average carbon number, and the average molecular weight. Properties of the average molecule are calculated similar to those provided by the n-d-M method (ASTM D 3238). These include percents aromatic, naphthenic, and paraffinic carbon, as well as the number of aromatic and naphthenic rings.