HIGH FRONT-END RESOLUTION COLLISION-INDUCED DISSOCIATION IN FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY

Several possibilities for obtaining high front-end resolution are demo nstrated, in particular for collision-induced dissociation. In order t o avoid residual excitation of the ion under investigation, it is nece ssary in such an experiment to avoid ejection of the nearby ions. This is why the ''difference'' method was used for the described experimen ts. The cyclotron frequency of an ion is dependent on its surrounding charge density; thus the number of ions in the cell must be drasticall y reduced if high front-end resolution is looked for. It is shown that under these conditions a front-end resolution of m/Delta m > 30 000 c an be reached for m/z 100. This can be obtained either by increasing t he selectivity of the excitation, using longer duration and lower ampl itude pulses, or by means of a two-dimensional experiment.