Abstract
Purpose: To determine the concentration of theobromine (TB) and caffeine (CF) in tea and other beverages using liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS).Methods: The extract of caffeine and theobromine from tea and other beverages was filtered by 0.45 μm nylon micro-syringe and then injected into a LC-ToF-MS system. Theobromine and caffeine were separated using Thermo Scientific C18-column (length 250 mm, width 2.1 mm and diameter 5 μm). Acetonitrile-methanol (ACN – MeOH, 3:1 v/v) was used as mobile phase B, while mobile phase A was 0.1 % FA in DIW. The volume injected was 30 μL at a rate of 0.3 mL/min.Results: Good linearity was obtained in the range of 0.3 – 400 and 0.2 – 200 mg/L for theobromine and caffeine, respectively (regression coefficient (R2) > 0.970). The limits of detection were 0.15 and 0.05 μg/mL for theobromine and caffeine, respectively. The highest concentrations of caffeine and theobromine determined in tea samples were 159.1 and 255.8 mg/L, respectively.Conclusion: Theobromine and caffeine have been successfully analysed in tea, coffee and soft drinks. LC-TOF-MS is an accurate and promising instrument for the determination of the studied compounds in beverages.Keywords: Theobromine, Caffeine, Tea, Coffee, LC-TOF/MS
Highlights
Methylxanthines, theobromine and caffeine are used as analgesics, diet aids, and cold/flu remedies in numerous popular carbonated drinks
Calibration curves were obtained by the plotting peak area of theobromine and caffeine separately against a working standard concentration
The results showed good linearity for caffeine and theobromine; in which (R2) was 0.979 and 0.999, respectively
Summary
Methylxanthines, theobromine and caffeine are used as analgesics, diet aids, and cold/flu remedies in numerous popular carbonated drinks. The analysis of theobromine and caffeine in foods, biological fluids, environmental samples, plants, and water, was provided with different instrumental methods, such as highperformance liquid chromatography (HPLC) [4], gas chromatography–mass spectrometry-flame ionization detection (GC–MS-FID) [5], Fourier transform-infrared spectrophotometry (FT-IR) [6], near-infrared spectroscopy [7], UV–Vis spectrophotometry [8], FT-Raman spectrometry [9], and capillary electrophoresis (CE) [10]. Of these techniques, HPLC which offers advantages, such as simplicity and selectivity coupled with a UV–Vis detector, was deemed the preferred analysis system for the analysis of theobromine and caffeine [8,11,12]. This limitation, and other challenges, can be resolved by coupling with a highly specific, sensitive, and accurate ToF-MS analyser that is considered a suitable and confirmative technology to measure trace levels of TB and CF
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