Electrocatalysis and Amperometric Detection at a Ruthenium-Modified Indium-Hexacyanoferrate Film Electrode

The electrocatalytic activity of a glassy carbon electrode modified with electrochemically deposited indium(III)-hexacyanoferrate (InHCF) film, which has been subsequently cycled in a solution of ruthenium(III), is described. Although the resulting ruthenium-modified InHCF thin film electrode behaves in a manner analogous to the parent InHCF film, its stability was found to be greatly improved. Such a modified electrode was characterized, in acidic (pH 2) 0.5 M KCl solutions, by cyclic voltammetry and flow injection analysis. It exhibits a high catalytic activity for the electrooxidation of some inorganic and organic compounds of analytical interest, such as As(III), S2O2–3, cysteine, and 2-furaldehyde. The analytical applicability of this novel ruthenium-modified InHCF film electrode for the amperometric detection in flowing streams is discussed. Repetitive sample injections with amperometric detection of thiosulfate at +0.8 V (vs. Ag/AgCl) as applied potential produced a stable response over 8 h of operation, making it very attractive for practical applications.