Linear ion trap mass selectivity with impulse power supply and sinusoidal dipolar excitation.

Abstract

An ion trap mass analyzer can be operated by either a sinusoidal waveform power supply or an impulse waveform power supply. The optimal conditions for the performance of ion trap which is driven by an impulse waveform power supply with sinusoidal dipolar voltage were investigated theoretically, and further verified by experiments. The analytical relationship between β and q values is derived theoretically for optimal performance, and the dependencies β(q) for different trapezoidal waveforms are studied. To explain the dependence of resolution with working point q, the derivative dβ/dq is also derived analytically for the case of a rectangular waveform power supply. The theoretical results are further verified by experiments. The results from both theoretical calculations and experiments are in very good agreement. The behaviour resolution with q is controlled by the dispersion dβ/dq that was also confirmed by experiments, when the resolution increases with q. The optimal conditions of β, qex values and required excitation time n are when S(q) is close to 1 for an ion trap driven by trapezoidal waveform voltage with sinusoidal dipolar voltage. It shown that with increasing impulse parameter τ the dispersion dβ/dq decreases and the mass resolution also decreases as result. In the case of applying a rectangular waveform shape voltage, the mass selectivity is the same as for the sinusoidal wave shape. Copyright © 2016 John Wiley & Sons, Ltd.