ELECTROCATALYTIC OXIDATION AND FLOW-INJECTION DETERMINATION OF REDUCED NICOTINAMIDE COENZYME AT A GLASSY-CARBON ELECTRODE MODIFIED BY A POLYMER THIN-FILM

G chemically modified electrode (CME) was prepared by electrochemical copolymerization of pyrrole and Methylene Blue. The resulting CME exhibits effective electrocatalytic activity towards the oxidation of reduced nicotinamide coenzymes (NADH and NADPH), with over a 400 mV decrease in the overvoltage. The effects of catalyst coverage and solution pH were examined. When the CME was used as a detector for flow injection ata constant potential of 0.25 V versus SCE, it gave detection limits of 2.5 x 10(-8) and 4.0 x 10(-8) mol dm(-3) for NADPH and NADH, respectively, with a linear concentration range of over four orders of magnitude. The CME retained a stable response for over 20 h in the dow system.