Electrochemical detection of NADH and dopamine in flow analysis based on tetraruthenated porphyrin modified electrodes

Modified electrodes with molecular films of a tetraruthenated cobalt-porphyrin complex have been employed in the amperometric detection of NADH and dopamine. The electrochemical oxidation of these bioanalytes can be monitored at the onset of the Ru-III/II redox wave (E degrees = 0.70 V vs Ag/AgCl), exhibiting a very sharp peak consistent with a rapid and efficient electron transfer process. Because of the rectifying properties of the molecular films, a high selectivity for reduced species has been observed in scanning measurements. Very good signal to noise ratios have been obtained in flow analysis, ensuring a detection limit in the ppb range, for NADH and dopamine.