Differential ion mobility separation in a linear RF ion trap operating at sub-ambient pressures

摘要

A linear ion trap is disclosed wherein an asymmetric voltage waveform (see Fig. 1) is applied to one or more of the electrodes forming the ion trap to cause ions to become radially separated in a first radial direction according to their differential ion mobility. The differential ion mobility separator is maintained at a pressure of less than 100 mbar. A symmetric RF voltage 4 is preferably also applied to at least some of said electrodes 3 so as to confine ions within said ion trap in a second orthogonal radial direction. A radially dependent axial potential barrier may be arranged at the exit of the ion trap (see Fig. 5) such that ions having a first differential ion mobility and a first radial displacement are retained axially within the ion trap but ions having a second differential ion mobility and a second radial displacement are ejected axially. Alternatively, ions separated according to their differential mobility may be ejected radially from the ion trap.