Process for the selective separation of electrically charged target molecules in an analytical mixture by means of capillary affinity gel electrophoresis, using a capillary tube which is at least partly filled with a polymer gel, whereby receptors for target molecules are covalently bound to the polymer, and an electric field of at least 50 volts/cm is applied, characterized in that (a) the capillary tube is charged with the analytical mixture, (b) in a first separation stage the target molecules in the analytical mixture are bound to the receptors and the remaining components are eluted, optionally while splitting open, and (c) in a second stage of the process the elution conditions are changed, optionally in stages, so that the affinity of the target molecules for the receptor is eliminated and the target molecules are eluted and detected, optionally whilst splitting open.
