Hollow porous molecularly imprinted polymers for rapid and selective extraction of cinnamic acid from juices

Rapid and selective extraction of target compounds from complex matrices was significantly important for their quantification. Here, hollow porous molecular imprinted polymers (HPMIPs) were prepared using cinnamic acid (CMA) as template, 4-vinylpyridine (4-VP) as functional monomer, and MCM-48 as sacrificial support. Hollow porous structure with large surface area (534.1 m2/g) made most recognition sites locate on the surface of HPMIPs, resulting in high binding capacity (14.84 mg/g) and fast kinetic binding (40 min). In comparison, binding capacity and binding equilibrium time for solid MIPs were 4.01 mg/g and 16 h. Equilibrium data fitted well to Freundlich equation, and adsorption process with multi-diffusion mechanisms could be described by pseudo-second order model. In addition, HPMIPs exhibited favorable selectivity. Finally, HPMIPs were successfully used as a molecular sorbent to efficiently and selectively extract CMA from apple and orange juices. Coupling with high-performance liquid chromatography and UV detection (HPLC–UV), the limit of detection for CMA was 0.006 mg/L, and the recoveries (89.3–103.5%) with RSD values ranged from 4.3% to 8.0% were relatively satisfactory. Results indicated the superiority of HPMIPs in the selective extraction field.