Simultaneous determination of caffeine, theobromine and theophylline in foods by HPLC

A method was developed for the simultaneous determination of caffeine (CF), theobromine (TB) and theophylline (TP) in various kinds of foods by HPLC. Solid foods except chewing gum were dialyzed for 1 hour against hot water, then for 5 hours against water at room temperature. CF, TB and TP in chewing gum were extracted with a blender into hot water. Liquid samples were diluted with 1% phosphoric acid. The test solutions described above were each passed through a BAKERBOND spe (SO3H) cartridge. The cartridge was washed with water and CF, TB and TP were eluted with a mixture of 2% ammonium solution-15% aqueous sodium chloride solution-MeOH (1:1:2). The three compounds were separated on a Cosmosil 5C18-AR column with a mobile phase of MeCN-0.01M phosphate buffer (pH 3.5) (1:9). Detection was done at 275 nm. The recoveries of CF, TB and TP added to various kinds of foods were 90 similar to 98%, 98 similar to 104%, 90 similar to 103%, respectively. The determination limits of CF, TB and TP were 10 mu g/g.