Electrochemical determination of NADH using a glassy carbon electrode modified with Fe3O4 nanoparticles and poly-2,6-pyridinedicarboxylic acid, and its application to the determination of antioxidant capacity

We have prepared a glassy carbon electrode modified with poly-2,6-pyridinedicarboxylic acid and with magnetic Fe 3 O 4 nanoparticles. This modification enhances the effective surface area and the electrocatalytic oxidation of nicotinamide adenine dinucleotide (NADH) in addition to providing positively charged groups for electrostatic assembly of the phosphate group of NADH. The modified electrode responds linearly to NADH in the range from 5 × 10 −8 to 2.5 × 10 −5  M and gives a lower detection limit of 1 × 10 −8  M. It displays satisfactory selectivity and reproducibility. The sensor was applied to rapid screening of plant extracts for their antioxidant properties. Poly-2,6-pyridinedicarboxylic acid (PDC) was fabricated by electropolymerizing 2,6-pyridinedicarboxylic acid with cyclic voltammetry (CV) on the glassy carbon electrode (GCE) surface. The magnetic Fe 3 O 4 nanoparticles treated with aminopropyltriethoxysilane (APTS) modified on the PDC/GCE to form APTS-Fe 3 O 4 /PDC composite film. The APTS-Fe 3 O 4 /PDC film had enhanced the effective electrode surface area and provided positively charged groups for electrostatic assembly of phosphate group of NADH.