Electrocatalytic determination of sulfite using a modified carbon nanotubes paste electrode: application for determination of sulfite in real samples

This paper introduces a carbon paste electrode modified with ferrocene and carbon nanotubes as a voltammetric sensor for determination of sulfite at pH 7.0. The results showed that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite occurred at a potential about 280 mV less positive than the unmodified carbon paste electrode. Kinetic parameters such as electron transfer coefficient (alpha) and heterogeneous rate constant (k) for sulfite were also determined using electrochemical approaches. Under the optimized conditions, the electrocatalytic oxidation peak current of sulfite showed two linear dynamic ranges with a detection limit of 0.1 mu M for sulfite. The proposed method was examined as a selective, simple, and precise method for voltammetric determination of sulfite in some real samples such as weak liquor from wood and paper industry, boiler water, river water, industrial water, and tap water.