Electrocatalytic Oxidation of Hydrazine at Glassy Carbon Electrode Modified with Electrodeposited Film Derived from Caffeic Acid

A caffeic acid modified glassy carbon electrode was constructed for the electrocatalytic detection of hydrazine. This modified electrode enabled hydrazine to be catalytically oxidized at a greatly reduced overpotential and in a wide operational pH range (pH 5.0–9.0). The overall number of electrons involved in the catalytic oxidation of hydrazine and the number of electrons involved in the rate determining step are 4 and 1, respectively. The rate constant for the catalytic reaction was evaluated by chronoamperometry, cyclic voltammetry and RDE voltammetry and was found to be around 10–3 cm s–1. Experiments were performed to characterize the electrode as an amperometric sensor for the determination of hydrazine and linear calibration plots were obtained over the range of 0.01 to 2.0 mM for linear sweep voltammetry and chronoamperometry. Amperometry in stirred solution exhibits a linear dynamic range of 2.5 μM to 1.0 mM (correlation coefficient 0.9993) and a detection limit of 0.4 M. The resulting modified electrode retains its initial response for at least 2 weeks if stored in phosphate buffer (pH 4). The precision of amperometry was found to be 1.8 % for replicate determinations of a 1.0 mM solution of hydrazine (n=12).