Synthesis and characterization of hollow porous molecular imprinted polymers for the selective extraction and determination of caffeic acid in fruit samples.

Hollow porous molecular imprinted polymers (HPMIPs) were prepared using caffeic acid (CA) as template, 4-vinylpyridine (4-VP) as functional monomer, and MCM-48 as sacrificial support. Large surface area (562.7m2/g) of HPMIPs resulted in high binding capacity (27.26mg/g) and fast kinetic binding (40min) in comparison with solid MIPs. Equilibrium data fitted well to Freundlich equation, and adsorption process with multi-diffusion mechanisms could be described by pseudo-second order model. Selectivity of HPMIPs was favorable. Finally, HPMIPs were successfully used to rapidly and selectively extract CA from fruits with a relatively satisfactory recovery (87.1-101.3%). Coupling with HPLC, contents of CA in kiwifruit, apple, papaya and waxberry were less than 1.0μg/g fresh fruit. Results indicated the superiority of HPMIPs in the separation field.