EFFECTS OF REACTANT ION KINETIC-ENERGY ON BOTH ENDOTHERMIC AND EXOTHERMIC ION-MOLECULE REACTIONS IN A QUADRUPOLE ION-TRAP MASS-SPECTROMETER

The effects of kinetic energy on the outcomes of exothermic and endothermic ion/molecule reactions in a quadrupole ion trap mass spectrometer are examined. Endothermic proton-transfer and charge exchange reactions may be driven in a quadrupole ion trap by acceleration of selected reactant ions to higher kinetic energies, via resonant power absorption from a supplementary a.c. voltage, prior to collisions with neutral substrate molecules. Reactions as endothermic as 1.1 eV for either proton-transfer or charge exchange processes have been promoted, with maximum conversion efficiencies of reactant ions to product ions ranging from 5 to 15% under optimized conditions. Depending on the nature of the reactant ion and its possible reaction pathways, activation of a selected ion may lead to a combination of collisionally-activated dissociation, ion loss from the trap by impingement upon an electrode or ejection, and endothermic ion/molecule reaction. Activation of reactant ions prior to exothermic ion/molecule reactions in the quadrupole ion trap results in decreased reaction efficiency, a result expected for translationally hot ions.