Using the patented Gradiflow system in conjunction with newly developed affinity membranes, the suitability of an electrokinetic technique for affinity fractionation was investigated. Blue dextran incorporated into an affinity membrane was used to deplete a solution of horse serum of albumin, with the result that a majority of serum proteins were enriched tenfold relative to albumin. The technique, when fully developed, would offer some advantages over affinity chromatography, since to a degree it is possible to control which components of the sample are presented to the affinity matrix. Furthermore, the technique would extend the capabilities of the already multifunctional Gradiflow system.