Surface molecularly imprinted polymers for solid-phase extraction of (--)-epigallocatechin gallate from toothpaste

Surface molecularly imprinted polymers (SMIPs) have been synthesized to selectively determine (–)-epigallocatechin gallate in aqueous media. SMIPs were prepared using a surface grafting copolymerization method on a functionalized silica gel modified with β-cyclodextrin and vinyl groups. The morphology and composition of the SMIPs were investigated by scanning electron microscopy, Fourier transform-infrared spectroscopy and thermogravimetric analysis. In addition, the molecular binding capacity, recognition properties and selectivity of the SMIPs were evaluated. The imprinted polymers were found to have a highly specific recognition and binding capacity for (–)-epigallocatechin gallate in aqueous media which is the result of the hydrophobic properties of the β-cyclodextrin and the hydrogen-bonding interactions of methacrylic acid. The SMIPs were successfully employed as solid-phase extraction adsorbents prior to the HPLC determination of (–)-epigallocatechin gallate in toothpaste. The HPLC analysis had a linear dynamic range of 0.5–50.0 μg·mL−1 with a correlation coefficient of 0.9998 and the recoveries ranged from 89.4% to 97.0% with relative standard deviations less than 4.8%. The limit of detection and limit of quantification were 0.17 and 0.33 μg·mL−1, respectively. The method provides a promising approach for the preparation of selective materials for the purification and determination of complex samples.