Flow-injection analysis and voltammetric detection of NADH with a poly-toluidine blue modified electrode

Poly-Toluidine Blue film was prepared by electrooxidative polymerization at a glassy carbon electrode in a phosphate buffer solution. The resulting chemically modified electrode (CME) exhibited excellent electrocatalysis toward the oxidation of reduced nicotinamide coenzyme (NADH) with over a 450 mV decrease of the overpotential compared with that at a bare glassy carbon electrode. Two electrochemical determinations of NADH, cyclic voltammetry and flow injection analysis, were established based on the electrocatalytical performance of the resulting modified electrode. Under an identical determinate condition, the voltammetric detection for NADH gave a detection limit of 3.3 mumol L-1 with a linear concentration range of 9.1 mumol L-1 to 1.8 mmol L-1. As a detector in a flow-injection system, the CME gave a detection limit of 0.1 mumol L-1 for NADH with a linear concentration range of 1.0 mumol L-1 to 3.2 mmol L-1. Obviously, flow-injection analysis is superior to voltammetric detection in NADH determination for its lower detection limit and wider detectable linear range.