Synthesis and Application of Histidine-Modified Poly(Glycidyl Methacrylate/Ethylene Glycol Dimethacrylate) Sorbent for Isolation of Caffeine from Black and Green Tea Samples

This work presents the synthesis of a polymeric mixed-mode solid-phase extraction (SPE) sorbent for clean-up and isolation of caffeine from black and green tea samples. The material was synthesized by a simple thermallyinitiated copolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate. Further functionalization was executed with histidine (HIS). Functional groups were investigated by attenuated total-reflection infrared spectroscopy. Furthermore, nitrogen sorption porosimetry was executed and revealed surface areas of 90m(2)g(-1). Adsorption capacities for caffeine were compared between functionalized and non-modified polymers and showed maximum capacities of 3.01 and 4.82mgg(-1) polymer, respectively. Time adsorption profiles revealed an equilibrium adsorption after 15min. The proposed polymer was used for SPE of black and green tea extracts and showed excellent clean-up efficiency for isolation of caffeine with recoveries ranging from 89 to 93%. When compared to commercially available Oasis HLB, the HIS-functionalized polymer demonstrated a distinctly better performance for clean-up. Finally, the proposed method was validated regarding international (ICH) guidelines and regulations.