Comparative evaluations of mass spectral databases.

This Communication presents a statistical analysis of the distributions of the National Institute of Standards and Technology/Environmental Protection Agencyj Mass Spectrometry Data Center Mass Spectral Database and the Wiley Registry of Mass Spectra according to sizes (peaks per spectrum) of spectra. The differences in the distributions are explained in terms of the different philosophies under which the two databases were built. The Wiley Registry is a collection that attempts to include all available spectra, including spectra of unique compounds derived from the literature. The NIST collection selects primarily spectra of interest for chemical analysis.