Cu-MOFs/GO composite-based electrochemical sensor for the simultaneous measurement of xanthine, hypoxanthine and caffeine at trace levels

Abstract

Copper-MOFs were prepared via a simple solvothermal route using copper metal ion as the source and trimesic acid as the linker molecule at room temperature. The composite was then prepared by mixing the copper-MOFs with graphene oxide and used as a modifier for the simultaneous measurement of xanthine derivatives, such as xanthine, hypoxanthine and caffeine. The composite was characterised by X-ray diffraction, infrared spectroscopy, thermogravimetry and BET surface area studies. The electrochemical behaviour of the composite was studied through cyclic voltammetry, impedance and square wave voltammetry. The analytical signal responses for all three analytes were linear in the concentration range of 1–400 μM, with limits of detection of 0.045, 0.052 and 0.02 μM for xanthine, hypoxanthine and caffeine, respectively. The sensor exhibited wide linearity, good stability and reproducibility and was successfully applied to measure target analyte molecules from real sample matrices at trace levels, even in the presence of common interferants. The fabricated sensor can be utilised as an alternative method for the simultaneous measurement of xanthine, hypoxanthine and caffeine in complex sample matrices at low concentration levels.