Abstract: An apparatus for the separation of macroion groups from a mixture utilizing a three field device for generating forces on the macroions including means for applying a centrifugal force, means for applying a magnetophoretic force, and means for applying a constant or variable electrophoretic force. In a separation step the centrifugal and magetophoretic forces assist in forming the macroions in separate groups of concentric bands on a rotating platform. The constant electrophoretic force may be optionally used to assist in this step. In an analytical step to characterize the mass and charge of the macroions, the electrophoretic and magnetophoretic forces are used to oppose the centrifugal force to control and hold the macroion bands at fixed positions on the platform. A band detection means is used to characterize the positions of the macroion bands on the platform. The variable electrophoretic force may be optionally used in a detection part of the analytical step.