Determination of caffeine and theobromine in tea, coffee, cocoa, and dietary supplements
The method is used for the determination of the mass fraction of caffeine and theobromine in tea and tea products, coffee and coffee products, cocoa and cocoa products, and dietary supplements.
Capillary electrophoresis method for the determination of the mass fraction of caffeine and theobromine is based on micellar electrokinetic chromatography (MEKC). Identification and quantitative determination of the components is performed by direct UV detection at the wavelength of 254 nm.
The measurement range for the components is 100 to 100 000 mg/kg (ppm).
Preservatives (sorbic and benzoic acids), sweeteners (acesulfame K, saccharin, aspartame, cyclamate), sodium glutamate, synthetic dyes, vitamins of the B group, vitamin C, vanillin in the concentrations that are typical for the products of interest does not influence the determination of the components.