Background-correction methods have been developed for the determination of caffeine in beverages, coffee and tea by second-derivative ultraviolet spectrophotometry. The second derivatives of caffeine were measured at 298.6 nm. Interference from tannins in beverages and tea was minimized by treating the sample with 0.1 m o l dm-3 sodium hydroxide and by precipitating tannins with copper(ti) acetate, respectively. Coffee samples were treated with sodium hydroxide (0.25-0.75 m m o l dm-3). The calibration graphs for the three types of sample had slightly different slopes (0.00146-0.00152 A nm-2 ppm-1) and linear ranges. The precision for the determination ranged from 0.3 t o 0.9%, at the 10 pg ml-1 level of caffeine. A number of cola drinks, energy drinks, lemon tea drinks, coffee samples and tea samples were analysed.
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