EXTENSION OF THE MASS RANGE OF A COMMERCIAL ION-TRAP USING MONOPOLAR RESONANCE EJECTION

The mass range of a commercial ion trap detector (ITD), Finnigan MAT M odel 800, has been extended by a factor of almost two through a simple modification to the ITD circuitry and to an end-cap electrode. Mass-r ange extension has been achieved by the addition of axial modulation a t an appropriate frequency applied asymmetrically on the end-cap elect rode during the mass scan. The experiments which are described show th at mass/charge measurements are accurate to better than 0.5% without e xternal calibration, and that a mass/charge range in excess of 1200 Da /charge is accessible.