Simultaneous separation and purification of (−)-epigallocatechin gallate and caffeine from tea extract by size exclusion effect on modified porous adsorption material

• Hydroquinone modified absorbents exhibited nanoscale microporous structure and high specific surface area.
• A novel synergistic effect between the size exclusion effect and hydrophilia was found on modified porous adsorbents.
• The size exclusion effect was used in separation and purification of EGCG and CAF from tea extract simultaneously.

A dual-task method for the simultaneous separation and purification of (−)-epigallocatechin gallate (EGCG) and caffeine (CAF) from crude extract of green tea was established by size exclusion effect onto hydroquinone modified porous adsorbents. The results showed that hydroquinone modified porous adsorbents P4 provided the best separation power due to it has more porous structure and phenolic hydroxyl group. The adsorption–desorption behaviors of EGCG and CAF onto P4 adsorbents were investigated. Adsorption kinetics of EGCG and CAF results showed that the adsorption followed the pseudo-second-order kinetic model. The results also indicated that the equilibrium adsorption data best fit the Langmuir model. Meanwhile, EGCG and CAF were separated successfully onto P4 adsorbents packed columns in a gradient eluent process, and P4 adsorbents exhibited the size exclusion effect for small molecules CAF. Based on the phenolic hydroxyl group and size exclusion effect of P4 adsorbents, the high purity EGCG and CAF were obtained with 40% (v/v) ethanol eluent successively. The process fulfilled the task of simultaneous separation and purification of EGCG and CAF, and proved to be a promising basis for preparations of difficult to obtain active components that have similar polarity and different sizes of molecules and derived from the same natural products.