Nickel oxide nanotubes-carbon microparticles/Nafion nanocomposite for the electrooxidation and sensitive detection of metformin.

The electrocatalytic oxidation of metformin was studied on a nickel oxide nanotubes-carbon microparticles/Nafion nanocomposite, using cyclic voltammetry and chronoamperometry. In the presence of metformin, the anodic peak current of the Ni(II)/Ni(III) transition increased, followed by a decrease in the corresponding cathodic currents. Based on the results, the drug was oxidized on nickel oxide nanotubes via an electrocatalytic mechanism. The catalytic rate constant, the electron transfer coefficient and the diffusion coefficient involved in the electrocatalytic oxidation of the drug were reported. A sensitive and efficient amperometric method was presented for the analysis of the drug, and the corresponding analytical parameters were reported. For metformin, a detection limit of 0.45 micromol L(-1) was obtained. The proposed amperometric method was also applied to the analysis of commercial tablets and the results were in good agreement with the declared values. Also, the applicability of the method to the direct assays of the drug in human serum and urine and breast milk was described. Copyright (c) 2010 Elsevier B.V. All rights reserved.