Rapid determination of theophylline, theobromine and caffeine in dietary supplements containing guaraná by ultra-performance liquid chromatography

Abstract

A rapid and simple method for determination of theophylline, theobromine and caffeine in dietary supplements containing guaraná by ultra-performance liquid chromatography (UPLC) has been developed. Theophylline, theobromine and caffeine were extracted from finely powdered samples with water in a boiling water bath for 20 min, then the extracts were filtered and the filtrates were subjected to UPLC. Liquid samples were diluted with water and filteres, and the filtrates were subjected to UPLC. UPLC separation was performed on an AQUITY UPLC BEH C 18 column (2.1 mm i.d.×50 mm, 1.7 μm, Waters) with 10 mmol/L ammonium acetate buffer (pH 4.0)-acetonitrile gradient and eluates were monitored at 275 nm. The recoveries of theophylline (spiked at 200μg/g [tablet] and 50/μg/mL [liquid]), theobromine (spiked at 200 μg/g [tablet] and 50μg/mL [liquid]) and caffeine (spiked at 1,000μg/g [tablet] and 250μg/mL [liquid]) were 97.6-98.7%, 97.3-99.7%, 97.1-105.4%, respectively. The quantitation limits of theophylline, theobromine and caffeine were 10μg/g (seed, seed powder, tablet and capsule) and 2.0μg/mL (liquid) each. When this analytical method was applied to commercial dietary supplements, theophylline, theobromine and caffeine were found at concentrations of 4.45 mg/tablet, 5.48 mg/tablet, 139 mg/tablet, respectively. Taking 4 tablets of this product according to the directions on the package could be dangerous to consumers because of possible overdosing of these ingredients.