Adsorption and reactivity of chlorogenic acid at a hydrophobic carbon ceramic composite electrode: Application for the amperometric detection of hydrazine

Sol-gel technique was used for construction of a carbon composite electrode. The prepared carbon ceramic electrode was modified with electroless deposition of chlorogenic acid for less than 1 min. The adsorbed thin films of chlorogenic acid on carbon composite electrode show one pair of peaks with a surface confined characteristic, which strongly depends on the solution pH, as anticipated for quinone/hydroquinone functionalities. The modified electrode shows highly catalytic activity toward hydrazine electrooxidation at wide pH range (5-11). Also the rotating modified electrode shows excellent analytical performance for amperometric determination of hydrazine. The detection limit, sensitivity, response time and linear dynamic range are 20 nM, 220 nA/muM, 1 second and 0.1 muM-1 mM, respectively. The catalytic rate constant for hydrazine oxidation at the surface of modified electrode was evaluated by cyclic voltammetry and was found to be around 1.5 x 10(3) M(-1)s(-1)in phosphate buffer solution (pH 8). The precision of chronoamperometric measurements was 1-3% for 5 replicate determinations in the concentration range of the linear calibration. The reproducibility of modified CCE was evaluated with 8 successive polishing and modifications and then the anodic peak current was measured (RSD 2%). The advantages of this sensor are excellent catalytic activity, high sensitivity, good reproducibility and simplicity of preparation at short time periods.