Analytical Sciences

Equilibrium Analysis of Reactions of Metal-Pyridylazoresorcinolato Chelates with Quaternary Ammonium Ion, Nonionic Surfactant and Polyethylene Glycol in Aqueous Solution by Capillary Zone Electrophoresis

Toshio TAKAYANAGI  and Shoji MOTOMIZU

Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushimanaka, Okayama 700-8530, Japan

The resolutions of metal-4-(2-pyridylazo)resorcinol chelates by capillary zone electrophoresis (CZE) were investigated in the presence of some interacting reagents; also, equilibrium reactions between the chelates and the interacting reagents were analyzed in an aqueous solution. Among nine metal chelates formed in aqueous solution, the chelates of V^V, Fe^II, Co^III, Ni^II, and Cu^II were resolved and detected by CZE, while other chelates were decomposed during electrophoretic migration. The electrophoretic mobility of the chelates of Fe^II, Ni^II, and Cu^II increased with increasing pH of the migrating solution; also, the acid-dissociation constants of these three chelates were determined by analyzing the mobility change. The ion-association constants of the five anionic chelates and pyridylazoresorcinolate ion with quaternary ammonium ions were also determined by analyzing the mobility change. The binding behavior of the ligand and its chelates with nonionic surfactant micelle, as well as with polyethylene glycol, were investigated, and their binding constants were determined through the mobility change. When Brij 35 was used as a nonionic surfactant interacting with the anionic chelates, the Fe^II chelate decomposed at Brij 35 concentrations over 6.67 mM. The equilibrium constants and the reactivity were compared with each other.

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