Electron capture dissociation in linear RF ion traps

摘要

The invention relates to the fragmentation of macromolecules in linear RF ion traps (LIT) through the process of electron capture disscoiation (ECD). The ion trap comprises a multipole, preferably quadrupole rod set 1-4, with ion repelling end electrodes, but alternatively may comprise an ion tunnel or helical ion trap. Low energy electrons generated by a thermionic filament 10 may be injected through an opening 8 in one of the pole rods 2, the electron source being kept at the highest positive potential which is achieved on the centre axis of the ion trap during the RF cycle. Alternatively, electrons may be injected through the gap between adjacent rods (see figure 5). Pulse-shaping of the RF voltages applied to the electrodes (see figures 2 and 6) offers longer periods of electron capture. The low energy electrons may also be guided by a magnetic field (see figures 7 and 8).