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

► Poly(thionine) modified preanodized SPCE lowers the overpotential for NADH oxidation. ► Ring-disk electrode is effective for simultaneous detection of NADH and H2O2. ► This biosensor can monitor both NADH and H2O2 in biological studies.