A continuous, hybrid magnetic field gradient device for colloidal magnetic affinity separation having an axially-rotating horizontal glass tube, and a plurality of axially located repeating magnetic units. Each magnetic units consists of an alternating current solenoid that surrounds the chamber followed by computer-controlled electromagnets carrying a direct current. The on-off cycle of the electromagnets is used to control the residence time of target-bound magnetic particles in the chamber thereby allowing the separate collection of the particle and target rich fractions and the target-lean fractions without interrupting the feed flow. The azimuthally flowing alternating current in the solenoid introduces transient axial and radial forces as well as torque on the magnetic particles, promoting mixing.