A method and apparatus for performing electrochemiluminescence assays are presented. In exemplary embodiments of the present invention an apparatus comprises an ECL-inactive electrode surface having a first assay-ligand immobilized thereon and an ECL-active microparticle having a second assay ligand immobilized thereon. In exemplary embodiments of the present invention a method comprises (a) forming a mixture comprising an electrochemiluminescent label and a microparticle having a first assay-ligand immobilized thereon, (b) applying electrochemical energy to an electrode surface in the presence of said mixture, and (c) measuring emitted electrochemiluminescence, where the microparticle is ECL-active and where the electrode surface is ECL-inactive when electrochemical energy is applied to it in the presence of said mixture.