Electrocatalitic Detection of Hydrazine Using Chemically Modified Electrodes with Cobalt Pentacyanonitrosylferrate Adsorbed on the 3–Aminopropylsilica Surface

Cobalt pentacyanonitrosylferrate on the aminopropylsilica silica gel surface (SiCoNP) was previously prepared following two steps. The electrochemical behavior of SiCoNP modified electrode showed two redox couples, the first and second redox couples were observed at anodic potential (Epa)1 = 0.36 and 0.60 V vs. Ag/AgCl attributed to the oxidation of Co(II) to Co(III) and Fe(II)(CN)5NO/Fe(III)(CN)5NO, respectively. The modified carbon paste electrode with SiCoNP was tested in the hydrazine electrooxidation. In the hydrazine electrooxidation, the H+ release was observed and the two metal centers are involved in this process. The proposed mechanism has been described and based on studies of the effect of hydrogen ion concentration in the redox process of bivalent compound formed. Thus a large increase in hydrogen ion concentration promotes the formation of an intermediate electroactive species with an anodic peak at 0.56 V. The nature of this species is not well established but may be related to protonation of cyanide or NO groups present. The modified graphite paste electrode presented a limit of detection of 2.38×10-4 mol L-1 and amperometric sensitivity of 1.37×10-6 A.mol-1.L.