Quantification of taurine in energy drinks using 1H NMR

Abstract

The consumption of so called energy drinks is increasing, especially among adolescents. These beverages commonly contain considerable amounts of the amino sulfonic acid taurine, which is related to a magnitude of various physiological effects. The customary method to control the legal limit of taurine in energy drinks is LC–UV/vis with postcolumn derivatization using ninhydrin. In this paper we describe the quantification of taurine in energy drinks by 1H NMR as an alternative to existing methods of quantification. Variation of pH values revealed the separation of a distinct taurine signal in 1H NMR spectra, which was applied for integration and quantification. Quantification was performed using external calibration (R2>0.9999; linearity verified by Mandel's fitting test with a 95% confidence level) and PULCON. Taurine concentrations in 20 different energy drinks were analyzed by both using 1H NMR and LC–UV/vis. The deviation between 1H NMR and LC–UV/vis results was always below the expanded measurement uncertainty of 12.2% for the LC–UV/vis method (95% confidence level) and at worst 10.4%. Due to the high accordance to LC–UV/vis data and adequate recovery rates (ranging between 97.1% and 108.2%), 1H NMR measurement presents a suitable method to quantify taurine in energy drinks.