Disclosed is a method for analyzing biological samples by immunofixation electrophoresis which involves immunodisplacement of target component(s) that may be present in the assayed biological sample, the target component(s) amounting to interfering component(s) when interpretation of the immunofixation results is considered. The immunodisplacement is carried out on an electrophoretic support that is preferably a gel, as defined herein. Accordingly, the invention provides IFE using an antibody or antibodies which is(are) modified (modified antibody) to bear additional negative electric charges, the modified antibody(ies) having antigenic specificity for a predetermined target immunoglobulin.