Molecularly imprinted polymer for pre-concentration of esculetin from tobacco followed by the UPLC analysis

Abstract

Molecularly imprinted polymers (MIPs) for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule. Polymers of varying composition were prepared using different monomers (4-vinylpyridine, methacrylic acid, and acrylamide), ethylene glycol dimethacrylate as the cross-linker, 2,2-azobis(2-methylpropinitrile) as the initiator, and different porogen solvents (ethanol, acetone/methanol, and acetonitrile). The best polymer was obtained when 4-vinylpyridine was used as the monomer and acetone/methanol (3:2) as the porogen solvent, whereas the template:-monomer:-cross-linker ratio was 1:4:20. The imprinting factor of the selected MIPs for esculetin was 3.77. The polymers were evaluated according to their selective recognition properties for esculetin and structurally-related compounds (esculin, scopoletin, coumarin, and 7-methoxycoumarin). Chemical and morphological characterizations of the polymers were investigated by FTIR and scanning electron microscope, which confirmed a high degree of polymerization. Surface area, pore volume, and pore size of the polymer were investigated by Brunauer-Emmett-Teller analysis. MIPs were also successfully used as solid-phase adsorbent materials for the extraction of esculetin from tobacco leaves. Esculetin contents in dried tobacco leaves were found to be (9.27±0.17) μg g-1.