Abstract: The present invention concerns methods for masking inhomogeneity of a member of a specific binding pair (sbp) employed in a capillary electroseparation. The method comprises binding the sbp member to synthetic particles that become localized during capillary electroseparation. Also disclosed is one embodiment of the present invention, which is a method for conducting a capillary electroseparation specific binding assay. The method involves the electroseparation of a labeled first member of a specific binding pair that is bound in a complex from labeled first member that is not bound in the complex. The complex comprises the first member and a second member of a specific binding pair. A combination is provided comprising a sample suspected of containing an analyte, a labeled first member of a specific binding pair, and a second member of a specific binding pair under conditions for forming a complex between labeled first member and the second member.