Abstract: The present invention relates to a method and apparatus for the separation of analytes based on their molecular weight, by application of an electric field across a low-friction matrix that includes with a charged separation agent. The matrix comprises charged regions ordered in a monotonous sequence distributed throughout the matrix so as to generate a charge density gradient. When an external electric field is applied, the complex will move through the different charged regions and focusing of different analytes in different charge regions will occur. These systems are suitable for planar, capillary in-tube electrophoresis, as well as multi-channel arrays of capillaries filled with charge gradient gels, serial arrays of discrete compartments with charge density gradient, arrays in a chip format, pre-designed mass focusing arrays for specific protein masses in application for protein and DNA marker diagnostics, and multi compartment trapping devices for specific mass ranges.