Abstract: A chemical mixture is conveyed to a multiple charging apparatus, where multiply charged ions are formed. The multiply charged ions are then conveyed to a mass spectrometer which generates mass/charge spectrum data relating intensity to a range of mass/charge values. This mass/charge spectrum data is transformed to generate mass spectrum data relating intensity to a range of mass values. Thereafter, a set of known masses are identified from the mass spectrum data by associating each peak intensity value in the spectrum with its molecular mass. Then a list of mass/charge ratios for each of the identified masses is formed and stored. Next, a range of mass/charge ratios for each mass value of the mass spectrum data is computed.