Analysis of xanthines in beverages using a fully automated SPE-SFC-DAD hyphenated system

Analysis of some xanthines (caffeine, theophylline and theobromine) in beve rages has been achieved by a fully automated on-line Solid Phase Extraction Supercritical Fluid Chromatography - Diode Array Detection (SPE - SFC - DA D). Three adsorbents have been tested for the SPE procedure: octadecyl modi fied silicagel (ODS) and two types of styrene-divylnibenzene copolymer base d materials, from which Porapack proved to be the most suitable adsorbent. Optimisation and correlation of both SPE and SFC operational parameters are also discussed. By this technique, caffeine was determined in ice tea and Coca-Cola in a concentration of. 0.15 ppm, theobromine - 1.5 ppb, and theop hylline - 0.15 ppb.