Ferrocenedicarboxylic Acid Modified Multiwall Carbon Nanotubes Paste Electrode for Voltammetric Determination of Sulfite

The electrocatalytic oxidation of sulfite has been studied by ferrocenedicarboxylic acid modified carbon nanotubes paste electrode. It has been found that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite is occurred at a potential about 350 mV less positive than that an unmodified carbon nanotubes paste electrode. The kinetic parameters such as electron transfer coefficient, alpha, and the catalytic reaction rate constant, k(h)(/), were also determined using electrochemical approaches. Also, electrochemical impedance spectroscopy used for study behavior of sulfite in aqueous solution. Using differential pulse voltammetric (DPV) method, the electrocatalytic oxidation peak current of sulfite shows a linear calibration curve in the range 0.6 - 100 mu mol L-1 of sulfite concentration. The detection limit (3 sigma) was determined as 0.3 mu mol L-1 by DPV method. The RSD% for 10.0 and 30.0 mu mol L-1 sulfite was 2.1% and 1.8%, respectively. The proposed method was examined as a selective, simple and precise method for voltammetric determination of sulfite in real samples with satisfactory results.