| Abstract: | Sterane analyses in petroleum geochemistry are normally based on mass spectrometric detection of major fragment ions. This method has limited specificity and is much improved by detection of parent or metastable transition ions. The latter provide a less complex picture and suggest a better analytical approach, although the technique has only limited mass resolution.Geochemical parameters calculated from mass spectrometric data are dependent on the method employed. Accepted values of these parameters will, therefore, show some variations with the techniques used.Internal standards are necessary for quantitative determination of components by mass spectrometry. A recommended approach is to use a stable isotope labelled analogue of the compound being determined with, in the case of deuterium, only three or four isotopic atoms introduced into the molecule. Too few isotopic atoms will result in interference from the natural isotopes and too many will give analytical deviations. |
