Simultaneous detection of NADH and H2O2 using flow injection analysis based on a bifunctional poly(thionine)-modified electrode

We report here a novel detection scheme for simultaneous detection of NADH and H2O2 based on a bifunctional poly(thionine)-modified electrode. Electropolymerization of thionine on a preanodized screen-printed carbon electrode effectively lowers the oxidation potential of NADH to 0.15 V (vs. Ag/AgCl). Since poly(thionine) is also a well known electrochemical mediator for H2O2 reduction, we further developed a poly(thionine)-modified ring disk electrode for simultaneous measurement of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) by flow injection analysis. By applying the optimized detection potentials of 0.2 V and -0.2 V at disk and ring electrodes, respectively, this system allows the simultaneous measurement of both analytes with good sensitivity (0.13 mu A/mM for H2O2 and 0.34 mu A/mM for NADH) and limit of detection (1.74 mu M and 26.0 mu M for NADH and H2O2). This opens the possibility of a whole series of biosensor applications. (C) 2011 Elsevier B.V. All rights reserved.