Sensitive and selective determination of tryptophan using a glassy carbon electrode modified with nano-CeO2/reduced graphene oxide composite

Abstract

Nano-CeO2/reduced graphene oxide (RGO) composite were successfully prepared using a simple electrochemical technique. The structure and morphology of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Numerous of CeO2 nanocrystals are found to be wrapped inside uniformly by gossamer like RGO. The electrochemical behaviors of tryptophan (Trp) on the glassy carbon electrode modified with nano-CeO2/RGO (nano-CeO2/RGO/GCE) were investigated by second derivative linear sweep voltammetry (SDLSV) and cyclic voltammetry (CV). It was found that high electrocatalytic activity was exhibited on the modified electrode for Trp oxidation. The peak current increased about 76-fold and the peak potential shifted 88 mV negatively at the nano-CeO2/RGO/GCE compared with that of the bare GCE, demonstrating the synergistic effect of nano-CeO2 and RGO on the electrode surface. The measurement parameters are optimized. Under the optimum conditions, a good linear relationship was observed between Trp oxidation peak current and its concentration in the range of 0.01–10 μM, with a sensitivity of 4.7306 μA μM−1 and the detection limit was obtained as 6.0 nM (S/N = 3) after accumulating at 0 V for 90 s. The developed method also exhibited good reproducibility, stability and anti-interference ability, and has been successfully applied to Trp detection in commercial compound amino acid injections, human serum and human urine samples with recoveries of 98.5%-106.0%.