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Computer programs using the Kendrick scale for calculating masses are described for rapidly assigning elemental formulas to ions in high resolution mass spectra. Output from the programs, based on nominal mass Z series, is displayed in the form of a rectangular array having 14 columns and a variable number of rows, depending on the number of peaks in a spectrum. This layout permits formulas for the major ions to be identified almost as fast as the output is obtained from the printer. The array is especially useful for displaying the spectra of complex petroleum fractions, where molecular ions for one thousand or more components may be detectable. All programs except one are written in FORTRAN 77 and are available from the author.
The utility of the programs is illustrated with output from the mass spectrum of a fraction known to contain one-ring aromatic neutrals separated from the 200 to 425°C distillate of the Cerro Negro (Eastern Venezuela) heavy petroleum. The fraction was found to consist mostly of hydrocarbons with Z numbers ranging from - 6 through - 16, where Z is defined by the formula CnH2n+z. Homologs in the -8 and -10 Z series were the most abundant. Only traces of oxygen- and nitrogen-containing compounds were found, but sulfur compounds having formulas CnH2n+zS with Z ⩽ -4 were found in significant quantities. These types of compounds are in agreement with those anticipated from the HPLC method used in the fractionation of the distillate.
fossil fuels, mass spectrometry, petroleum analysis, data processing
Senior chemist, IIT Research Institute, National Institute for Petroleum and Energy Research, Bartlesville, OK