In situ activated 3,5-dinitrobenzoic acid covalent attached to nanostructured platform for NADH electrooxidation

The activation of 3,5-dinitrobenzoic acid (3,5-DNBA) in situ is proposed for electrocatalytic detection of NADH at low overpotentials. Thus, 3,5-DNBA was strategically connected to a nanostructured surface based on MWCNTs and PEI (an amine rich polymer). Then, R–NO/R–NHOH was electrogenerated in situ by cycling the potential between 0.15 and −0.55 V versus SCE. The formation of an intermediate charge transfer complex is proposed for the reaction between NADH and redox mediator. The apparent Michaelis–Menten constant (KM) obtained by RDE voltammetry and amperometry was in good agreement, around 10−5 mol L−1. The kobs for the catalytic reaction evaluated by chronoamperometry and RDE voltammetry, was in good agreement and was found to be around 104 L mol−1 s−1. The sensor provides a linear response range for NADH from 4.0 up to 42.0 μmol L−1 with a sensitivity of 71 nA L μmol−1, detection and quantification limits of 1.2 and 4.0 μmol L−1 respectively, with a response time of 0.16 s.