Nafion covered lead film electrode for the voltammetric determination of caffeine in beverage samples and pharmaceutical formulations

This paper presents a sensitive, selective and low-cost voltammetric method for the determination of caffeine using a Nafion covered lead film electrode. The sensor was prepared on a glassy carbon electrode modified with lead film recovered by a Nafion layer. Caffeine was accumulated and then oxidised at the modified electrode surface to produce two anodic peaks at 0.86 and 1.40 V (vs. Ag/AgCl) in 0.1 mol L−1 H2SO4 medium. The obtained detection limits for caffeine following 120 s of accumulation time were equal to 1.7 × 10−8 mol L−1 (for peak 1) and 2.2 × 10−7 mol L−1 (for peak 2). The method was successfully applied to determination of caffeine in tea, coffee, soft and energy drink samples as well as pharmaceutical formulation and the contents closely corresponded to those quoted by the manufacturer and those obtained by the reported spectrophotometric method.