The Electrochemical Behavior of Iron(III) Incorporated in Zeolite Y-Modified Electrode and the Catalytic Oxidation of Ascorbic Acid

Abstract

A new method is developed for the catalytic oxidation of ascorbic acid (AA) at a graphite-zeolite-modi®ed electrode doped with iron(III) (Fe 3 YaZCME), in which iron(III) exchanged in zeolite Y can act as catalyst to oxidize AA. First, the electrochemical behavior of iron(III) incorporated in the zeolite Y-modi®ed electrode was studied. The results illustrate that diffusion controls the ferricaferrous redox process at the Fe 3 YaZCME. The anodic current of this process increases with the supporting electrolyte concentration of non-size-excluded cation and was suppressed when using size-excluded cation. Second, the catalytic oxidation of AA was explored at Fe 3 YaZCME. With constant potential amperometric measurements optimal conditions for AA determination were obtained. The working potential was 0.55 V (vs. SCE); the supporting electrolyte was 0.1 M KNO 3 or 0.05 M Na 2 HPO 4 -KH 2 PO 4 buffer solution (pH 6.8). The response current exhibits a linear relationship with the concentration of AA over the range of 1.58610 À6 ±2.15610 À2 M. When samples of urine, and fruit were analyzed with Fe 3 YaZCME, we obtained AA recovery of 98±102%, and a relative standard deviation lower than 3%. Meanwhile, interferences from other ions and organic substances were examined.