Application of simultaneous excitation/detection to generate real-time excitation profiles in Fourier transform ion cyclotron resonance mass spectrometry

Simultaneous excitation/detection (SED), which permits observation of ion m otion during an excitation event, is used to generate real-time Fourier tra nsform ion cyclotron resonance (FTICR) excitation profiles that track the r adial extent of ion motion in a trapped-ion cell. The conventional FTICR ex citation profile is collected in a series of individual experiments in whic h peak magnitude is monitored as excitation voltage is increased. In contra st, SED permits the single-scan detection of ion cyclotron motion within th e trapped-ion cell and consequently yields the data that produces a real-ti me excitation profile. Data analysis techniques are presented that facilita te conversion of a time domain SED profile into an excitation profile. An o rder of magnitude decrease in the amount of time is required to acquire an excitation profile, while the precision of the measurement is improved. To demonstrate the utility of the technique, it is applied to the study of axi al and radial ion loss mechanisms for argon, benzene, and acetophenone ions under different conditions. SED excitation profiles are also used to illus trate the facility of quadrupolar excitation for minimizing radial ion loss . (C) 2000 American Society for Mass Spectrometry.