Sulfite Oxidation Mediated by Ortho-Phenylenediamine / Co(ii)-Tetrakis(para-Aminophenyl)porphyrin Copolymers in Acid Medium

Abstract

The aim of this work is to study the sulfite oxidation mediated by glassy carbon electrodes modified with copolymers formed by ortho-phenylenediamine (OPD) and Co(II)-tetrakis(para-aminophenyl)porphyrin (CoTAPP). The copolymer was obtained through continuous cycling of potential of a glassy carbon electrode in acid medium containing each respective homopolymer in 1:1 feeding volume, in which the ortho-phenylenediamine concentration was 1·10 -1 M and the CoTAPP concentration was 1·10 -4 M. The film obtained is thin, stable and contains a low amount of porphyrin in comparison to the amount in orthophenylenediamine. Its electrocatalytic activity was tested toward the sulfite oxidation. In this case, this film is more electrocatalytic than the modified electrode modified with the CoTAPP electropolymer, even though ortho-phenylenediamine is inactive in this reaction. In this work the electrocatalysis process, the morphology of the film, and the difference of electrocatalytic behavior between the ortho-phenylenediamine and cobalt porphyrin homopolymers and the orthophenylenediamine-porphyrin copolymer were studied. The morphologic studies were done using Au electrodes since the electrocatalytic activity on Au and on glassy carbon are quite similar.

Sensor for Quantitative Analytical Determination of Sulphite in Wine Using a System of Modified Electrode and a Membrane Absorption System

“…These species are formed by an irreversible oxidation process [25]. It calls the attention the excellent electrocatalytic activity of the copolymer toward the sulfite oxidation, what must be due to the presence of Co in the porphyrin structure [26]. According to the feeding during the copolymerization process, the pophyrin content in the copolymer is 1000 times less than its content in OPD, but between both monomers there must be some kind of interaction that allows for the displacement of the wave potential of the sulfite oxidation, just as it displaces the potential of the Co redox couple and the phenazine/phenacile redox couple.…”