Self calibration approach for mass spectrometry

A method for analyzing mass spectral data, comprising:

• acquiring profile mode mass spectral data containing at least one ion of interest whose elemental composition is to be determined;
• obtaining a correct peak shape function based on an actually measured peak shape of at least one isotope of an ion having an elemental composition that is not initially known, where said at least one isotope is one of a baseline resolved monoisotope or other isotope with an insignificant contribution from minor isotopes;
• generating at least one possible elemental composition for the at least one ion of interest;
• calculating a theoretical isotope distribution for said elemental composition and a theoretical isotope cluster by applying the same correct peak shape function to the theoretical isotope distribution;
• and
• comparing quantitatively the corresponding parts of said theoretical isotope cluster to that from the acquired profile mode mass spectral data to obtain at least one of elemental composition determination, classification, or quantitation for said at least one ion of interest.