A quality index for reference mass spectra

A numerical rating for evaluating the quality of reference mass spectra used for retrieval and interpretive applications is proposed. The overall quality index is the product of seven quality factors: (1) source of the spectrum; (2) ionization conditions; (3) higher molecular weight impurities; (4) illogical neutral losses; (5) isotopic abundance accuracy; (6) number of peaks; and (7) lower mass limit of peaks. For quality factor 6 the number of peaks of abundances ≥1% was found to correspond to 15 more than the number of atoms in the molecule with a correlation coefficient of 0.482. The program has been found useful in preparing a data base of 41429 mass spectra; for the majority of spectra judged to be unsatisfactory by the program this arose from a low quality factor 6 value (too few peaks).