Standard caffeine solutions at different concentrations were analysed by means of HPLC (Dionex P680) equipped with UVD 170U detector and Acclaim 120 C18 column as described previously and results were used as calibration graph. Caffeine sample extracted was diluted with hot deionized water, filtered under vacuum, cooled and analysed for caffeine by HPLC. 4?l of the sample
were injected into the instrument. It was determined at 272nm wavelength, 30% (v/v) acetonitrile solution for mobile phase and 0.8ml/min flow rate.