DETERMINATION OF ION-LIGAND BOND-ENERGIES AND ION FRAGMENTATION ENERGIES OF ELECTROSPRAY-PRODUCED IONS BY COLLISION-INDUCED DISSOCIATION THRESHOLD MEASUREMENTS

A triple quadrupole mass spectrometer adapted for the determination of collision-induced dissociation (CID) threshold energies of ions produced by electrospray (ES) is described. The ES-produced ions are transferred from 1 atm to a low pressure source, 10 Torr, where they can be partially declustered and after that thermalized by gas collisions. The ions entering the vacuum of the triple quadrupole are not accelerated in the front end of the apparatus in order to avoid ion/gas molecule collisions which will induce an increase of the internal energy of the ions and broaden the kinetic energy (KE) profile of the ions. Nevertheless, KE broadening is observed. It is demonstrated that it originates in Q(1) and is due to the radial d.c. field of the quadrupole. The KE broadening is attributed to ion/gas molecule collisions in Q(1). In spite of this effect, threshold energy, E(0), determinations can be obtained to an estimated accuracy of approximately 0.2 eV.