Densitometric determination of caffeine in tea beverages after TLC separation

Thin layer chromatographic separation with densitometric detection has been used for quantitative determination of caffeine in different tea beverages prepared from green, oolong, pu-erh, and black tea. Chromatographic separation on 60 17,51 silica gel layers was performed with chloroform-ethyl acetate-formic acid, 5 + 4 + 1, (v/v/v) as a mobile phase. The spots were developed densitometrically at lambda = 280nm. The method was validated in terms of selectivity, stability of the analyte, linearity, precision, and limits of detection and determination. The level of caffeine in different manufactured teas decreased in the order: black tea > oolong congruent to pu-erh > green tea. Under the established experimental conditions repeatable and accurate results were obtained. The method was simple, reliable, economical, and convenient for isolation and quantification of caffeine in tea beverages.