Enhancement of the analytical properties and catalytic activity of a nickel hexacyanoferrate modified carbon ceramic electrode prepared by two-step sol-gel technique: application to amperometric detection of hydrazine and hydroxyl amine

The electroless sol-gel technique was used for the construction of nickel hexacyanoferrat (NiHCF) modified carbon composite electrodes (CCEs). This involves two steps: formation of a carbon ceramic electrode fabricated by nickel powder and then immersing the electrode into a sodium-hexacyanoferate solution for the immobilization of NiHCF films. The cyclic voltammety of the resulting modified CCEs prepared under optimum conditions, shows a well defined surface redox couple due to the [(NiFeIII/II)-Fe-II(CN)(6)](-2/-1) system. The effect of different alkali metal cations in Supporting electrolyte on the behavior of the modified electrode were Studied. The charge transfer coefficient (alpha) and charge transfer rate constant (Q for modified films were calculated. Hydrazine and hydroxylamine have been chosen as a model to elucidate the electocatalytic ability and analytical parameters of NiHCF modified CCE prepared by one and two-step sol-gel techniques and these compounds determined amperometically at the surface of modified electrodes. The latter shows a good electocatalytic activity towards the oxidation of hydrazine and hydroxylamine in the pH range 3-8 in comparison with CCEs modified by homogeneous mixture of graphite powder, Ni(NO3)(2) and Na-2[Fe(CN)(6)], (one-step sol-gel technique). Furthermore, the catalytic rate constant, linear dynamic range. limit of detection, and sensitivity for hydrazine and hydroxylamine detections were evaluated and compared with CCEs prepared with one-step sol-gel method. The modified CCEs containing NiHCF shows good repeatability, short response time, t 90% < 3 s, long term stability (3 months) and excellent catalytic activity. Furthermore, the method of preparation is rapid and simple and the modified electrodes are renewed by simple mechanical polishing and immersing in [Na3Fe(CN](6)] Solution. (C) 2003 Elsevier B.V. All rights reserved.