Abstract
Ion/molecule reactions were explored in a newly developed miniature mass spectrometer fitted with a rectilinear ion trap (RIT) mass analyzer. The tandem mass spectrometry performance of this instrument is demonstrated using collision induced dissociation (CID) and ion/molecule reactions. The latter includes Eberlin transacetalization reactions and electrophilic additions. Selective detection of the chemical warfare simulant dimethyl methyl phosphonate (DMMP) was achieved through selective Eberlin reactions of its characteristic phosphonium fragment ion CH~3~OP^+^(O)CH~3~ (m/z 93), with 1,4‐dioxane or 1,3‐dioxolane. Efficient adduct formation as a result of electrophilic attack by the phosphonium ion on various nucleophilic reagents, including 1,1,3,3‐tetramethyl urea, methanesulfonic acid methyl ester, dimethyl sulfoxide and methyl salicylate, was also observed using the RIT device. The product ions of these reactions were analyzed using CID and the characteristic fragmentation patterns of the ionic addition products were recorded using multiple‐stage experiments in the miniature RIT instrument. This study clearly demonstrates that a small, home‐built, miniature RIT mass spectrometer can be used to perform analytically useful ion/molecule reactions and also that instruments like this have the potential to provide a portable platform for in situ detection of organophosphorus esters and related compounds with high specificity using tandem mass spectrometry. Copyright © 2005 John Wiley & Sons, Ltd.