Use of ion-molecule reactions for selected reaction monitoring in gas chromatographic/tandem mass spectrometric analyses in two model systems.

The use of ion-molecule reactions with NH3 for selected reaction monitoring (SRM) in gas chromatographic/tandem mass spectrometric analysis is demonstrated for 2-methoxyethanol and chlorobenzene in methanol and urine. In the former, the reaction [CH3OC2H4]+ + NH3----[H2NC2H4]+ + CH3OH was followed; in the latter, the reaction [-C3H5Cl]+. + NH3----[C6H5NH3]+ + Cl.. Increased selectivity and an improvement in sensitivity by factors of up to five were observed when compared to conventional SRM analyses that used collisionally activated decompositions on NH3. SRM analyses with a triple quadrupole tandem mass spectrometer using ion-molecule reactions rather than collisionally activated decompositions have been found to be more sensitive and more selective in two model systems.