A mass peak profile generation model to facilitate determination of elemental compositions of ions based on exact masses and isotopic abundances

To identify elemental compositions of ions, a mass peak profile generation model (PGM) was developed to plan data acquisitions and to interpret the data obtained by using a high resolution mass spectrometer (VG70-250SE). The PGM provides a list of all compositions possible for the exact mass of ion M and its error range from which the user selects a hypothetical composition. The PGM then plots [M + 1] and [M + 2] mass peak profiles and calculates masses and abundances of full and partial [M + 1] and [M + 2] profiles relative to the M profile. All possible compositions, calculated values for the exact masses and relative abundances, and measures of profile broadening and the shape of the [M + 2] profile are listed in a table. Pass-fail results for each of six criteria based on a comparison between table entries for the hypothetical composition and each of the other compositions are indicated. Compositions failing one or more criteria will be eliminated if the hypothetical composition is correct. The table provides assurance that all possible compositions based on the elements specified by the user have been considered. The PGM can be used to estimate the minimum resolution and number of determinations necessary to identify the correct composition by eliminating all others. As multiple determinations are made and error limits become smaller, average values are entered into the PGM to determine all compositions consistent with the data, often until only one composition remains. (C) 1997 American Society for Mass Spectrometry