Amperometric flow-injection analysis of hydrazine by electrocatalytic oxidation at cobalt tetraphenylporphyrin modified electrode with heat treatment

Chemically modified electrodes prepared by treating the cobalt tetraphenylporphyrin modified glassy-carbon electrode at 750° (HCME) are shown to catalyze the electrooxidation of hydrazine. The oxidation occurred at +0.63 V vs. Ag/AgCl (saturated potassium chloride) in pH 2.5 media. The catalytic response is evaluated with respect to solution pH, potential scan-rate, concentration dependence and flow-rate. The catalytic stability of the HCME is compared with that of the cobalt tetraphenylporphyrin adsorbed glassy-carbon electrode. The stability of the HCME was excellent in acidic solution and even in solutions containing organic solvent (50% CH 3OH). When used as the sensing electrode in amperometric detection in flow-injection analysis, the HCME permitted sensitive detection of hydrazine at 0.5 V. The limit of detection was 0.1 ng. The linear range was from 50 ng to 2.4 μg. The method is very sensitive and selective.