One-step synthesis of chiral molecularly imprinted polymer TiO2 nanoparticles for enantioseparation of phenylalanine in coated capillary electrochromatography.

ABSTRACT

A novel chiral molecularly imprinted polymer TiO2 nanoparticle was synthesized in one step for the enantioseparation of phenylalanine in coated capillary electrochromatography. To the author's knowledge, the chiral molecularly imprinted nanomaterials have still not been reported, to date. Chiral molecularly imprinted TiO2 nanomaterials (L-PHE@MIP(APTES-TEOS)@TiO2) were used as a chiral stationary phase to separate the phenylalanine enantiomers in coated capillary electrochromatography (CEC). The imprinted coating was prepared from L-phenylalanine (L-PHE) as the template, TiO2 nanoparticles (NPs) as the support substrate, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, and tetraethyl silicate (TEOS) as the cross-linker. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for the characterization of the L-PHE@MIP(APTES-TEOS)@TiO2@capillary. Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were employed for the characterization of the L-PHE@MIP(APTES-TEOS)@TiO2. The effects of the applied voltage, pH value, buffer concentration, and acetonitrile content were investigated  experimentally to determine the optimum conditions for CEC. The best resolution for  phenylalanine enantiomers by CEC reached a value of 3.48. In addition, the specific recognition effect of L-PHE@MIP(APTES-TEOS)@TiO2 on PHE enantiomers was studied by selective experiment. Finally, adsorption kinetic research, adsorption equilibrium isotherm study, and adsorption thermodynamic experiment were carried out to investigate the separation mechanism of PHE enantiomers with the L-PHE@MIP (APTES-TEOS)@TiO2@capillary, and the results were consistent with those of CEC experiments.