Octacyanomolybdate-doped-poly(4-vinylpyridine) ionomer film electrode for the electrocatalytic oxidation of l-ascorbic acid

摘要

Poly(4-vinylpyridine) (PVP)-based anion exchange polymers are not studied as much as cation exchange polymers Nafion and Eastman Kodak AQ for electroanalytical applications. Similarly, octacyanomolybdate [Mo(CN)8 4?] has not been studied much as a redox mediator. This communication presents results from examinations of the behaviour of Mo(CN)8 4?-doped PVP ionomer film electrode to highlight the opportunities for realization of the application of this composite electrode for l-ascorbic acid (AH2) estimation via electrocatalytic mediation in acidic medium. The modified electrodes were characterized by cyclic voltammetry and rotating disc electrode voltammetry. PVP coatings possess strong anion-binding capacity for Mo(CN)8 4? mediator with an extraction coefficient of 990, and electrostatically cross-linked PVP films offer insignificant resistance to permeation of AH2, facilitating a cross-exchange reaction between the substrate and the mediator in the entire film volume. They show effective electrocatalytic oxidation of AH2, with the oxidation potential of AH2 decreased by ～200 mV in overpotential compared to that at bare electrode. Mo(CN)8 4?/PVP composite electrode does not respond to the more common interferents of l-ascorbic acid estimation even at high positive potentials. These and several other attractive potentialities of the modified electrode are demonstrated by direct determination of AH2 in a commercial vitamin C tablet without any special treatment, with the value closely agreeing (±0.75%) with the reference method.