Synthesis and characterization of porous surface molecularly imprinted silica microsphere for selective extraction of ascorbic acid

Abstract

Molecularly imprinted polymers (MIPs) with core-shell structure for efficient, reliable, and selective extraction of ascorbic acid (AA) were developed via co-polymerization process based on acrylamide (AM) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, 2,2'-azobis(2-methylpropionitrile) (AIBN) as initiator, and AA as template. The inorganic core comprised of amino-functionalized silica microspheres (AFSM) was prepared by co-condensation of tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane) (APTMS) in a water-in-oil (W/O) macroemulsion. The synthesized materials were characterized by IR-ATR, SEM, and N2 adsorption–desorption isotherm. The binding properties and selectivity of the AFSM@MIP and AFSM@NIP (i.e., non-imprinted polymers) were demonstrated by adsorption capacity and imprinting factor obtained based on UV–Vis absorption measurements. Furthermore, synthesis conditions were optimized such that imprinting efficiency and adsorption capacity were maximized. Finally, it was demonstrated that generated MIP core-shell hybrid microspheres provide rapid adsorption with high binding capacities (up to 5.08 mg g−1), excellent imprint factors, and exceptional reusability. A comparative study using AFSM@MIP and AFSM@NIP for simultaneous extraction of AA and citric acid (CA), allowed verifying the excellent selectivity of AFSM@MIP, which presented an imprinting factor of 2.30.