Patent attributes
A method and device for separating ions according to their ion mobility are disclosed. An ion guide is provided having a plurality of electrodes arranged to form an ion guiding path that extends in a closed loop. RF voltages are supplied to at least some of the electrodes in order to confine ions within said ion guiding path. A DC voltage gradient is maintained along at least a portion of a longitudinal axis of said ion guide, wherein the voltage gradient urges ions along the ion guide such that the ions separate according to their ion mobility as the ions pass along the ion guide. As time progresses the portion of the ion guide along which the DC voltage gradient is maintained is moved along the ion guide. An ion exit region is provided which moves around said ion guide such that ions exit said ion guide at different locations at different times. The present invention allows ions to exit the ion guide after the ions have been separated and without having to wait until the ions reach a fixed exit point, by which time the ions may re-merge with other ions.
