Detection of catechin based on its electrochemical autoxidation

Catechins are strong autoxidant to produce steady intermediate in alkali solution. In present work, we, for the first time, developed a electrochemical method based on ruthenium tris (2, 2′) bipyridyl (Ru(bpy)₃³⁺) modified boron-doped diamond (BDD) electrode to investigate the electrochemical reduction of catechin autoxidation intermediate with its existence verified by the electron spin resonance (ESR). The reduction peak potential was observed at −855.5 mV, not appearing either in acid solution (pH 2) containing catechins or in oxidized catechin solution (pH 12). Moreover, the effects of pH, ascorbic acid, Cu²⁺, Fe²⁺ and autoxidation time are investigated, demonstrating the reduction peak being really the reduction of catechin autoxidation intermediate. It is found that the peak current is proportional to scan rate, indicative of a surface confined reduction process. Sensitive amperometric response was obtained covering linear range from 0.3268 μM to 0.1591 mM. The determination of catechin in commercial preparations using this method shows satisfactory results comparable with those of the traditional methods.