Electrochemical behavior of rhodium acetamidate immobilized on a carbon paste electrode: a hydrazine sensor

The electrochemical behavior of rhodium acetamidate immobilized in carbon p aste electrode and the consequences for sensor construction were evaluated. The electrode showed good stability and redox properties. Two reversible r edox couples with midpoint potentials between 0.15 and 0.55 V vs SCE were o bserved. However, peak resolution in voltammetric studies was very dependen t on the supporting electrolyte. The correlation between coordinating power of the electrolyte and peak potential suggests that the electrolyte can co ordinate through the axial position of the complexes. Furthermore, the axia l position may be also the catalytic site, as a catalytical response was ob served for hydrazine oxidation. A good linear response range for hydrazine was fit by the equation i = 23.13 (+/- 0.34) c, where i = current in mA and c = concentration in mel dm(-3) in the range of 10(-5) up to 10(-2) mel dm (-3). The low applied potential (<300 mV) indicates a good device for hydra zine sensor, minimizing interference problems. The short response time (sim ilar to 1 s) may be useful in flow injection analysis. Furthermore, this sy stem was very stable presenting good repeatability even after 30 measuremen ts with a variance of 0.5 %.