Preparation of polypyrrole films containing ferrocyanide ions deposited onto thermally pre-treated and untreated iron substrate: Application in the electroanalytical determination of ascorbic acid

A polypyrrole containing ferrocyanide ions Fe(CN)63− (FCN) as doping anions were prepared by anodic electropolymerization onto iron and onto thermally pre-treated iron electrodes, in an aqueous solution containing pyrrole, potassium hexacyanoferrate (K4Fe(CN)6) and potassium tetraoxalate (C4H3KO8). The electrochemical behaviour of these modified electrodes was studied by cyclic voltammetry method. The electrostatic ability of these modified electrodes (PPy/FCN/Fe and PPy/FCN/Fe3O4/Fe) was demonstrated towards the oxidation of ascorbic acid (H2A). The results show that Fe(CN)63− anions incorporated into the PPy matrix improve the electrocatalytic activity of these films. The (PPy/FCN/Fe3O4/Fe) modified electrode showed greater ability and redox electroactivity than the (PPy/FCN/Fe) modified electrode and than the unmodified Fe electrode. It has been found that under optimum pH condition (pH 7), the oxidation of ascorbic acid at the surface of PPy/FCN/Fe3O4/Fe occurs at a potential about 200 mV less positive than at PPy/FCN/Fe and at Fe surfaces. The catalytic oxidation peak current showed a linear dependence on the ascorbic acid concentration and a linear calibration curve was obtained in the range 0.5–9 mM of ascorbic acid with a correlation coefficient of 0.9994 and good sensitivity (0.24 μA/μM). The detection limit (2σ) was determined and found to be equal to 0.15 mM.