Because biomolecular interactions play important role in the physiological and pathological phenomena at molecular level, there is a great need to develop new techniques and tools for biological studies as proved by active on-going research. Surface proton resonance and related biosensors have been actively and successfully employed in numerous studies for the characterization of macromolecular interactions.  However, even though such valuable techniques are available, new microsystems and miniaturized instrumental tools are highly desirable to provide complementary and even totally new information.  The flexible nature of capillary electromigration techniques makes them versatile tools for numerous biological interaction, purification and separation studies. To help in the elucidation of the biological interactions, adsorption energy distribution calculations, first introduced to our quartz crystal microbalance studies [1, 2] were utilized also in partial filling affinity capillary electrophoresis. With the help of this new tool, the degree of heterogeneity of the adsorption can be determined prior to the rival model fitting procedure.