Electrocatalytic oxidation and ion chromatography detection of S₂O₃^2-, SO₃^2-, I^- and SCN^- at glassy carbon electrode with functionalized multi-wall carbon nanotubes film

In this research, a glassy carbon electrode modified with the functionalized multi-wall carbon nanotubes (MWNT-COOHs) film was used as an amperometric sensor for the determination of S₂O₃^2-, SO₃^2-, I^- and SCN^-. The electrochemical behavior of those oxidizable inorganic anions at this modified electrode was studied by means of cyclic voltammetry (CV). The experimental results indicate that the modified electrode exhibits a high electrocatalytic activity towards the oxidation of those anions with a relatively high sensitivity, a good stability and a long-life. Separated by ion chromatography (IC) with 1.25 mmol/L H₂SO₄ as an eluent, those oxidizable anions can be determined by the MWNT-COOHs modified electrode successfully. Under the optimal chromatographic conditions, the detection limits are 1.5×10^-7 mol/L for S₂O₃^2-, 2.5×10^-7 mol/L for SO₃^2-, 1.2×10^-7 mol/L for I^- and 2.0×10^-7 mol/L for SCN^-, respectively. The method was applied successfully to the determination of those anions in environmental water.