Electrocatalysis of NADH oxidation using electrochemically activated fluphenazine on carbon nanotube electrode

• Fluphenazine is electrochemically oxidized to a redox active compound.
• MWCNTs are preferred for formation of a redox active fluphenazine derivative.
• Electroactivated fluphenazine possesses activity toward the oxidation of NADH.
• LOD and linear range of NADH determination were 5 μM and 15–84 μM, respectively.

Electrocatalytic determination of NADH using a hybrid surface-modified electrode with multi-wall carbon nanotubes (MWCNTs) and a novel electrogenerated redox mediator is described. The redox mediator precursor — fluphenazine (Flu) was adsorbed on MWCNT-modified glassy carbon (GC) electrode which was then subjected to electrochemical activation in 0.1 M H2SO4 using cyclic voltammetry (CV) over a range of potentials − 0.2 to 1.5 V vs. Ag/AgCl (6 scans at 100 mV s− 1). Cyclic voltammograms of Flu indicated the formation of a stable electroactive material presenting one reversible redox couple at the formal potential of − 0.115 vs. Ag/AgCl in a phosphate buffer (pH 7.0) as a supporting electrolyte. The peaks increased linearly with increasing scan rate indicating electroactive molecules anchored to the electrode surface. The GC/MWCNT/Flu electrode efficiently catalyzed the oxidation of NADH with a decrease in the overpotential of about 600 mV and 150 mV compared to the bare GC and GC/MWCNT electrode, respectively. This modified electrode was successfully used as the working electrode in the chronoamperometric analysis. The peak current response to NADH was linear over its concentration range from 15 μM to 84 μM, and correlation coefficient 0.998. The limits of detection (5 μM) and quantitation (15 μM) were evaluated.