The critical evaluation of a comprehensive mass spectral library.

A description of the methods used to build a high quality, comprehensive reference library of electron-ionization mass spectra is presented. Emphasis is placed on the most challenging part of this project--the improvement of quality by expert evaluation. The methods employed for this task were developed over the course of a spectrum-by-spectrum review of a library containing well over 100,000 spectra.

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.

Photodecomposition of Chloromethanes Adsorbed on Silica Surfaces.

Irradiation of CCl, CFCl, and CFCl in the presence of CH in vessels containing silica sand or fused quartz tubing results in the formation of chlorine-containing products. The formation of these compounds occurs at wavelengths extending up to approximately 400 nm, that is, at wavelengths well beyond the absorption threshold of the chloromethanes in the gas phase. It is suggested that CCl adsorbed on silica surfaces photodissociates to yield CCl and CCl species.