Voltammetric Determination of Caffeine in Energy Drinks Using an Electrode Modified with a Nafion Film and Mixed-Valence Iridium Oxides

It is found that mixed-valence iridium oxides electrodeposited on the surface of a glassy carbon electrode exhibit catalytic activity in the oxidation of caffeine. In this case, a more pronounced catalytic effect is obtained on an electrode modified with a composite based on a film of a perfluorinated sulfopolymer (Nafion) and mixed-valence iridium oxides. A selective voltammetric method for the determination of caffeine is developed. A linear logarithmic dependence of current on the caffeine concentration is observed in the range from 1 × 10 –8 to 5 × 10 –3 M. The developed method was used to determine caffeine in energy drinks.