An automated micellar electrokinetic capillary chromatographic method has been developed in order to determine xanthines, e.g. caffeine, theobromine and theophylline, and chlorogenic acid in samples of yerba mate (Ilex paraguariensis). The target constituents were detected by photodiode array, and quantified by an external standard method. In addition, each constituent was collected separately and identified by EIMS. The method has been used to analyse 30 samples of mate infusions prepared at 30 and 75 degrees C with milled leaves and stems of 14 commercial brands which had been subjected to different elaboration processes. Suspended powdered material of each infusion was also analysed after three sieving steps. There was a remarkable difference in the relative xanthine composition of the finely suspended material, the amount of which varied according to the yerba mate brand, the elaboration process and the temperature of the infusion. The importance of these results with respect to gastrointestinal disorders which have been observed by habitual consumers of mate are discussed.

Micellar electrokinetic capillary chromatography (MECC) experimental conditions were applied to 12 samples of methylxanthine-containing infusions of different commercial brands of yerba mate, coffee, tea and cocoa as well as two cola drinks. The best resolution in this mode of automated high-performance capillary electrophoresis (HPCE) was achieved here when using 15 kV voltage in an uncoated fused-silica capillary of 45 cm length (40 cm effective length), 50 mM sodium dodecylsulfate, 90 mM pH 8.5 borate buffer and UV detection. Theobromine, caffeine and theophylline were separated, and the peak splitting due to tautomeric species was observed. Experimental conditions were controlled, keeping constant the size of the elution window in each analysis. The limit of detection was less than 1 mg l −1 , the limit of quantitation was 2.5 mg l −1 and the work range was 2.5-300 mg l −1 . This HPCE-MECC system has proved suitable for the analysis/quality control of xanthines in beverages for consumption. Roles of various parameters as well as distinctly charged species of each xanthine and the origin of peak splitting in this MECC system are discussed.

No abstract