Theoretical and numerical analysis of the behavior of ions injected into aquadrupole ion trap mass spectrometer

A numerical simulation method has been developed for the analysis of trappi ng ions injected into an ion trap mass spectrometer. This method was applie d to clarify the effects of the following parameters on trapping efficienci es: (1) initial phase of the radio frequency (RF) drive voltage, (2) ion in jection energy, and (3) RF peak voltage while injecting ions. The following conclusions were obtained by theoretical and simulation approaches. 1. The second and third dominant oscillations contribute significantly to t he trapping mechanism of the injected ions, even for low q values. 2. A formula relating the operating parameters, which gives the maximum tra pping efficiency, is derived. 3. Based on the above-mentioned formula, an advanced injection method is pr oposed, in which the RF peak voltage is decreased while injecting ions, The ability of this method to solve the problem of unequal sensitivity among d ifferent ion species is indicated by numerical simulation. Copyright (C) 2000 John Wiley & Sons, Ltd.