A method and apparatus for the fraction sorting of cells is provided. The invention include a dispensing device, aspirating device, flow channel and a magnetic assembly. A first fractional sorting device includes a dipole fractional cell sorter. The dipole fractional cell sorter includes large aspect ratio flow channel and a dipole magnetic assembly. A second fractional sorting device includes a quadrupole fractional cell sorter. The quadrupole fractional cell sorter includes an annular flow channel having inlet and outlet splitters, and a quadrupole magnetic assembly. The quadrupole magnetic assembly includes pole pieces having projecting members with convex surfaces and in is in physical communication with the annular flow chamber. The method of the present invention provides a flow through fractional cell sorting process which is based on the application of a magnetic force to cells having a range of magnetic labeling densities.