No abstract

The copper tetraphenylporphyrin (CuTPP) was prepared within a NaY zeolite cavity to investigate the electrocatalytic behavior of CuTPP upon the oxidation of hydrazine and cysteine. The amount of 0.067 mmol g ¹1 of CuTPP was obtained in the zeolite cavities. Cyclic voltammetry showed only an anodic peak at 320 mV that was assigned to the oxidation of Cu I to Cu II . This peak was not affected by the supporting electrolyte nature or by solution pH. The electrode showed electrocatalytic activity to oxidize both cysteine and hydrazine, however for cysteine the activity was weak, possibly as a result of the adsorption of oxidation product (cystine). Although hydrazine oxidation was efficient, neither oxidation was diffusion controlled. A linear correlation between catalytic current and hydrazine concentration allows sensing of hydrazine in the 0.2 × 10 ¹6 to 1.0 × 10 ¹6 mol L ¹1 concentration range. The detection limit was 1.0 × 10 ¹7 mol L ¹1, and the response time was 1.1 s. The sensor was stable for at least 6 months under continuous use.