▎ 摘　　要

Graphene (G) and graphene oxide (GO) were used to modify a glassy carbon electrode (GCE) in order to enhance electron transfer. The best results were obtained when the electrode surface was modified with a thin film of GO dispersed in an aqueous chitosan solution. The resulting electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The optimized electrode was applied for the determination of ascorbate in synthetic and natural samples. The sensitivity to ascorbate is 247 +/- 8 mu A cm(-2) mmol(-1) L, and the limit of detection is 13 nmol L-1. The limit of detection is better than that of other sensors. The data obtained by the new method for ascorbate detection in juice were in a good agreement with the data provided by the producer.