Determination of caffeine and glucose in selected energy drinks

Abstract

The aim of this study was to monitor the caffeine and glucose content in several energy drinks. The caffeine was determined by (direct) differential pulse voltammetry at a glassy carbon paste electrode in 0.5 mol L–1 sulfuric acid at a potential step of 5 mV, potential amplitude of 40 mV, and the scan rate of 50 mV s–1. The content of glucose was determined using amperometric glucose biosensor in 0.1 mol L–1 phosphate (pH 7.0) buffer solution at a constant voltage of +0.4 V and stirring speed of 400 min–1. The selected samples were analysed and the results obtained compared to those declared by manufactures. Except to three samples, namely "Monster", "Red Bull" (without sugar) and "Spark", the individual results were in good agreement with the declared amounts. Moreover, based on the analyses performed, it can be stated that the energy drinks "Big Shock!" and "Red Bull" are the best source of energy when considering the found total sugar via the glucose content.