Electrochemical reduction of SO2 on poly-Co-3-tetraaminophenylporphyrin glassy carbon modified electrode

This article describes the electrochemical reduction of sulfite in water-ethanol mixtures under acidic conditions on a glassy carbon electrode modified with a conducting film formed by Co(II) tetra-3-aminophenyl porphyrin. Rotating disc electrode experiments show a kinetic limitation related with the formation of an adduct between the reduced porphyrin and the sulfur compound. UV-Visible spectroelectrochemical data suggest that Co(I) is not stabilized; thus the adduct should involve a radical species of the porphyrin. However, the resulting modified electrode is stable and shows a linear relationship between current and concentration of the sulfur species at pH 1. The detection range of sulfite by the modified electrode goes from 12 to 150 mg L-1. The detection limit is 4.15 mg L-1.