Analysis of Petroleum Hydrocarbons by Mass Spectra

In technical analysis of gases and liquids a mass spectrometer has been used chiefly as a quantitative analysis apparatus and there have been few attempts to apply the spectrometer to qualitative analysis. The reason is that qualitative analysis of mixtures by the use of a mass spectrometer does not work well. Due to the recent development of a gas chromatograph, however, we are now able to separate many compounds into their individual components. Our idea is to combine the use of a gas chromatograph with that of a mass spectrometer: we first separated sample compounds into their components by the use of the former and then we attempted to make a qualitative analysis of these components by the use of the mass spectra of the latter. As for the above qualitative analysis by the use of mass spectra, we used the method of identifying each hydrocarbon through the pattern coefficients of mass spectra. We divided mass spectra into several groups and determined a base peak in each group. Next we calculated the ratio of each peak to the base peak and then changed the obtained ratio into its logarithm. Then we plotted logarithms against mass numbers (M/e) and thus we succeeded in identifying the type of each hydrocarbon.