Voltammetric sensor for caffeine based on a glassy carbon electrode modified with Nafion and graphene oxide

We report on a voltammetric sensor for caffeine that is based on a glassy carbon electrode modified with Nafion and graphene oxide (GO). It exhibits a good affinity for caffeine (resulting from the presence of Nafion), and excellent electrochemical response (resulting from the pressence of GO) for the oxidation of caffeine. The electrode enables the determination of caffeine in the range from 4.0 x 10(-7) to 8.0 x 10(-5) mol L-1, with a detection limit of 2.0 x 10(-7) mol L-1. The sensor displays good stability, reproducibility, and high sensitivity. It was successfully applied to the quantitative determination of caffeine in beverages.