Gas-phase ion-molecule reactions: a model for the determination of biologically reactive electrophilic contaminants in the environment.

A promising instrumental technique has been investigated to rapidly screen complex environmental samples for chemical contaminants having the propensity to covalently bond to biomacromolecules such as DNA. Radical molecular ions of pyridine, a model compound for nucleophilic bases of DNA, were mass-selected and allowed to react with electrophilic environmental contaminants in the collision cell of a triple quadrupole mass spectrometer. Analytes were introduced into the collision cell via a gas chromatographic column. Reactive chemicals are then characterized by scanning Q3 to identify associative reaction products. A good qualitative correlation was observed for the gas-phase reactivity of a series of electrophilic reagents with both their alkylating reactivity in solution (4-(4-nitrobenzyl)pyridine) and AMES test mutagenicity which had been previously published. Femtomole limits of detection for specific associative reaction products were demonstrated. Gas-phase reactions of ions of environmental contaminants (introduced into the source) with neutral pyridine (in the collision cell) were also investigated. Reactions of the radical molecular ion of the allyl reagents with neutral pyridine were similar to results from the mass-selected reaction of the pyridine radical molecular ion with neutral allylic reagents.