Calculation of the information content of retrieval procedures applied to mass spectral data bases

A procedure has been developed for estimating the information content of retrieval systems with binary-coded mass spectra, as well as mass spectra coded by other methods, from the statistical properties of a reference file. For a reference file, binary-coded with a threshold of 1% of the intensity of the base peak, this results typically in an estimated information content of about 50 bits for 200 selected m/z values. It is shown that, because of errors occuring in the binary spectra, the actual information content is only about 12 bits. This explains the poor performance observed for retrieval systems with binary-coded mass spectra. (Auth.)