Determination of the binding constants of tricomponent interaction systems by capillary electrophoresis

The determination of the binding constants of tricomponent systems has been developed based on the measurement of the change of migration time of metal (central) ion at different concentration of a ligand in the two competitive interaction systems. As examples, The apparent binding constants of zinc ion with cysteine and tartaric acid system, and zinc with cysteine and lactic acid system have been obtained. The binding constants of two zinc species to cysteine have been compared. This method could be applicable to measure the binding constant of two ligands competitive interaction systems.