Collision-induced dissociation of mobility-separated ions using an orifice-skimmer cone at the back of a drift tube

An ion mobility-mass spectrometry technique that incorporates a differentia lly pumped orifice-skimmer cone (OSC) region at the exit of the drift tube has been developed. The OSC region is similar in design to those used in el ectrospray ionization sources and offers improvements in ion transmission ( by factors of similar to5-10 compared with previous designs) and the abilit y to induce fragmentation of mobility-separated ions. The separation of ion s prior to dissociation at the skimmer cone allows the origin of fragment i ons to be examined. Here, we describe the experimental design and demonstra te the approach by examining fragment ions that are common to multiple char ge states and different gas-phase ion conformations of electrosprayed angio tensin II and [Sar(1), Val(5), Ala(8)] angiotensin II peptides.