Evaluation of the phenolic antioxidants of olive (Olea europaea) leaf extract obtained by a green approach: Use of reduced graphene oxide for electrochemical analysis

Deep Eutectic Liquids (DELs) have been specially designed, and used for the extraction of bioactive natural products from a bio-waste, since they have attracted much attention from economic and ecological aspects. In this study, an easy, accurate and sensitive detection method has been developed towards a trace amount of oleuropein which is one of the most significant components of the olive leaf extract. TiOx-modified reduced graphene oxide electrode (TiOx-RGO@GCE) has been used as the sensing electrode for the quantitative detection of oleuropein. The structural characterization of TiOx-RGO@GCE has been performed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and atomic force microscopy (AFM) techniques. Cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques have been implemented to investigate the electrochemical behavior of oleuropein. The electrochemical experiments revealed that the quasi-reversible reaction is the dominant mechanism on the electrode/electrolyte interface. The linear concentration range of 1-12 mu M was obtained with the detection limit of 18.7 nM for oleuropein.