Patent ID: 7633060

Claim:
A method of separating ions, comprising: a) radially confining ions within an interior of a multipole by generating an RF field; b) generating an axial DC field within the multipole interior, the magnitude of the DC field increasing with distance from a central axis; c) mass selectively exciting ions within a first m/z range to cause the radial extents of the motion of the excited ions to increase in a first transverse plane; and d) mass selectively exciting ions within a second m/z range to cause the radial extents of the motion of the excited ions to increase in a second transverse plane different from the first transverse plane; whereby the excited ions within the first m/z range are caused to move toward a first end of the multipole, and the excited ions within the second m/z range are caused to move toward the second, opposite end of the multipole.