INVESTIGATION OF LOW-VOLTAGE ON-RESONANCE ION SELECTION FOR FOURIER-TRANSFORM MASS-SPECTROMETRY

Low-voltage on-resonance ion selection (LOIS) was recently introduced as an alternative technique for ion selection and storage. Under high pressure conditions and similar to the technique of quadrupolar axiali zation, unwanted (unselected) trapped ions are eliminated from the ana lysis cell through collisions with cell plates following orbital expan sion. The ions remaining after tens of seconds of mass selection can b e detected with better coherence, leading to improvements in ion detec tion and sensitivity. Here, experiments designed to test ion remeasure ment and ion transfer capabilities are presented. Simulations of ion m otion give insight into the possible mechanism of ion cooling, which d oes not appear to be the same as that of the axialization process. Bec ause of its ease of use, lack of need for additional hardware devices, and comparable ion selection results, LOIS is an attractive alternati ve for trapped ion experiments. (C) 1998 American Society for Mass Spe ctrometry.