The electrocatalytic oxidation of hydrogen peroxide has been studied by iodide at the surface of carbon paste electrode. Cyclic voltammetry and chronoamperometry techniques were used to investigate the suitability of iodide as a mediator for the electrocatalytic oxidation of hydrogen peroxide in aqueous solution with various pH. Results showed that pH 8.00 is the most suitable for this purpose. The kinetic process of the catalytic reaction can be explained using cyclic voltammetry and chronoamperometry. The calculated mean value of catalytic rate constant (kh) is determined to be 6.46 × 102 M−1s−1 using chronoamperometry data. In order to obtain the diffusion coefficient of iodide, chronoamperometry method has been used, that the value of D has been calculated 7.16 × 10−1 cm2 s−1. The catalytic oxidation peak current was linearly dependent on the hydrogen peroxide concentration and the linearity range obtained was 1.00 × 10−5 to 1.00 × 10−3 M. Detection limit has been found to be 5.61 × 10−6 M (3σ;). This method can provide a simple and low cost electrochemical sensor for catalytic oxidation detection of hydrogen peroxide in real sample.

The poly(m-toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO 4 , also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m-toluidine)/ modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 mM (S/N ¼ 3). The catalytic reaction rate constant, (k h ), was calculated 5.5 Â 10 2 M À1 s À1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.