Mechanistic studies and sensitive determination of norepinephrine at a nafion/lead-ruthenium oxide pyrochlore chemically modified electrode

Nafion/Lead-ruthenium oxide pyrochlore (Pb2Ru1.75Pb0.25O7-y) chemically mod ified electrode (NCME) exhibits excellent electrocatalytic response towards the norepinephrine (NE) oxidation reaction. NE oxidation by CV studies sho w the following main features: i) elechochemical oxidation of NE to o-quino ne derivative (Al), ii) intramolecular cyclization of o-quinone derivative to leucodopachrome derivative, iii) further oxidation to dopachrome (A2), a nd iv) formation of polymeric melanine like products. Controlled product an alysis using UV-visible spectroscopy gives evidence of the participation of leucodopachrome derivative (lambda = 425 nm) intermediate. The electrocata lytic oxidation process of Al is mediated by the electrochemically active R u-VI present in the pyrochlore network. The electrocatalytic reaction follo ws the Michaelis-Menten type kinetics, similar to an enzymatic mechanism. T he determination of NE on the NCME was performed using square-cave voltamme try. A linear calibration plot was obtained over 0-6 muM with a detection l imit (3 sigma) of 7.44 nM. The NCR IE showed high stability and no marked i nterference in the presence of glucose, ascorbic acid, and oxalic acid.