A New Redox Mediator (Cupric-Neocuproine Complex)-Modified Pencil Graphite Electrode for the Electrocatalytic Oxidation of H2O2: A Flow Injection Amperometric Sensor

This paper introduces the cupric-neocuproine complex ([Cu(Nc)(2)](2+)) as a new redox mediator for the electrocatalytic oxidation of H2O2. For this purpose, [Cu(Nc)(2)](2+) was modified onto a disposable pencil graphite electrode (PGE) surface by using Nafion (Nf) as a cation-exchange membrane for the effective adsorption of complex. The modified electrode was prepared by immersing Nf-adsorbed PGE into [Cu(Nc)(2)](2+) complex solution (0.40 mM of Cu2+ and 0.80 mM of Nc prepared at pH 4.76 in 0.10 M acetate buffer). SEM images and EDX spectra of electrodes were presented for the elucidation of their surface morphologies. Cyclic voltammetric results showed that H2O2 was electrocatalytically oxidized at [Cu(Nc)(2)](2+)/Nf/PGE, because both the increase in current and the potential shift to a more negative direction were observed for oxidation of H2O2 at [Cu(Nc)(2)](2+)/Nf/PGE in comparison to bare PGE. Then, the electrocatalytic activity of [Cu(Nc)(2)](2+)/Nf/PGE toward H2O2 oxidation was utilized for amperometric determination of H2O2 in flow injection analysis (FIA) system. Flow injection (FI) amperometric studies showed two linear calibration ranges (1.0-1000.0 mu M (R-2=0.9958) and 1000.0-10000.0 mu M (R-2=0.9902) with a detection limit of 0.4 mu M H2O2 which is considered good for electroanalytical determinations, especially for electrocatalytic oxidation. To test the applicability of the developed FI amperometric hydrogen peroxide sensor, H2O2 contents of some relevant samples were determined.