MULTIPOLE STORAGE ASSISTED DISSOCIATION, A NOVEL IN-SOURCE DISSOCIATION TECHNIQUE FOR ELECTROSPRAY-IONIZATION GENERATED IONS

In this work we present a novel in-source dissociation scheme referred to as multipole storage assisted dissociation (MSAD) for electrospray ionization (ESI) generated ions in which dissociation is effected by employing extended ion accumulation intervals in a high pressure rf-on ly hexapole assembly prior to mass analysis. Following an extended ion accumulation interval in which ions are confined in the rf-only hexap ole, ions are gated out of the hexapole, trapped, and mass analyzed in the trapped ion cell of a Fourier transform ion cyclotron resonance ( FTICR) mass spectrometer. The accumulation region is comprised of an r f-only hexapole ion guide which separates two electrodes, a biased ski mmer cone, and an auxiliary 'gate' electrode at the low pressure end o f the hexapole, This technique should be applicable to other mass spec trometry platforms compatible with pulsed ionization sources including quadrupole ion traps, and time-of-flight mass analyzers. This concept is demonstrated with the dissociation of a small protein in which sel ective fragmentation is observed at labile amino acid linkages produci ng primarily y-type fragment ions. (C) 1998 John Wiley & Sons, Ltd.