Qualitative and quantitative analysis of energy drinks using H NMR and HPLC methods.

Energy drinks (EDs) are widely consumed to stimulate psychomotor functions and improve the efficiency of the human body. They typically contain caffeine, taurine, sugars or sweeteners, vitamins and organic acids. EDs were selected for the study in terms of composition diversity, reflecting the variety of products available on the Polish market. The analysis of the composition of energy drinks was performed using H NMR spectroscopy, HPLC-DAD, titration and refractometric methods. Diagnostic signals in H NMR spectra of the citric acid, caffeine and niacinamide were used for quantitative analysis. The citric acid content in energy drinks ranged from 140 to 780 mg per 100 mL. The niacinamide content in the tested energy drinks varied from 3.4 to 9.7 mg per 100 mL and was usually higher than it was reported on the label. The amount of caffeine (from 19 to 40 mg) was slightly lower than labeled. Quantitative determinations by H NMR and HPLC are compatible and can be successfully used interchangeably. In the so-called "sugar-free" drinks, no simple sugars or sucrose were found, thus H NMR can easily and quickly recognize ED without the addition of sugar. Our studies showed that H NMR spectroscopy is a valuable tool for quality control of energy drinks.