Gold-copper metal-organic framework nanocomposite as a glassy carbon electrode modifier for the voltammetric detection of glutathione in commercial dietary supplements

Abstract

An electrochemical sensor based on a gold-copper metal-organic framework immobilized on the surface of glassy carbon electrode has been developed for the electrocatalytic oxidation and determination of glutathione. Gold nanoparticles were incorporated into copper-1,3,5-benzenetricarboxylate and the composition and structure of the resulting nanocomposite (Au@Cu-BTC) were verified by transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffractometry, scanning electron microscopy and Fourier transform infrared spectroscopy. Cyclic and square wave voltammetric studies of the electrochemical behavior of glutathione at the modified electrode showed that the incorporation of gold particles increased the conductivity of Cu-BTC. Glutathione was detected by the formation of a Cu (II)-glutathione complex and its subsequent oxidation at ca. + 0.25 V vs. Ag/AgCl. The proposed methodology exhibited a low limit of detection (0.30 μmol L−1) and a wide linear dynamic range (1–10.0 μmol L−1) with good sensitivity (0.89 ± 0.02 μA μmol L―1) and repeatability (2.14 %). The high recovery (98.2 %) obtained in the analysis of a dietary supplement renders this new approach very attractive for the analytical determination of glutathione in commercial samples, particularly if the technique is extended to commercially produced screen-printed electrodes.