Separation of Various Alkaloids by Ion Exchange Resin. VIII

Separation of Xanthine Bases by Ion Exchanger Chromatography

Abstract

Separation of xanthine bases by ion-exchanger chromatography was attempted using a weak-acid type cation exchanger (R-H form). When a phosphate buffer of around pH 7 was used as the desorption solution, dimethylxanthine (theobromine and theophylline) and trimethylxanthine (caffeine) were separated but mutual separation of dimethylxanthine isomers was difficult. When a strong-acid type cation exchanger (R-H form) was used and eluted with buffers of pH 7-1.6, theophylline and theobromine were separated but not theophylline and caffeine. Gradient elution using hydrochloric acid as a desorption solution, with increasing acidity, effected elution of theobromine, theophylline, and caffeine, in that order, and their separation was quantitative. When weak bases, such as xanthines, are to be separated from each other, it is more effective to elute at a low pH because dissociation of a weak base would be more complete in that range. Medium-acid type cation exchanger was found to be unsuitable for quantitative separation because of greater tailing.