Electrocatalytic Oxidation of Some Hydrazine Compounds at Glassy Carbon Electrode Modified with Co-Gluconate Complex

Cobalt oxyhydroxide modified glassy carbon electrodes (GC/Co) prepared by anodic electrodepostion in alkaline solution containing gluconate ions as ligand species have been characterized and proposed as sensing probes for the detection of hydrazine compounds. Under cyclic voltammetry and chronoamperometric conditions, the electrooxidation processes of hydrazines on the GC/Co are severely attenuated indicating strong and irreversible adsorption of the analyte on the electrode surface with subsequent formation of stable films with fouling effects on the catalytic sites. On the contrary, under flowing conditions the hydrazine compounds show well-defined and reproducible peaks with good analytical performance. Flow injection analysis (FIA) carried out at constant applied potential of 0.3 V vs. Ag/AgCl (4 M?KCl) and using a flowing stream of 0.1 M NaOH solution containing 50 mu M Co2L22- as on-line modifier, shows limits of detection (LODs) comprised between 0.5 mu M for hydrazine and 2 mu M for 1,2-dimethyhydrazine. Regression analysis, shows linear ranges spanning over about three orders of magnitude above the detection limits with coefficients of correlation better than 0.96.