Synthesis of molecularly imprinted polymer using attapulgite as matrix by ultrasonic irradiation for simultaneous on-line solid phase extraction and high performance liquid chromatography determination of four estrogens

A molecularly imprinted polymer was synthesized by ultrasonic irradiation, with attapulgite as matrix using β-naphthol as the template molecule, acryloyl-β-cyclodextrin as the functional monomer, and N,N-methylenebiacrylamide as the cross-linking agent, respectively. The imprinted polymer was characterized by infrared spectroscopy and transmission electron microscopy. Compared to polymers prepared by traditional heat sources, the molecularly imprinted polymer synthesized by ultrasonic irradiation had better selectivity and faster adsorption kinetics to estriol, estradiol, estrone and diethylstilbestrol. Using the imprinted polymer as the packing material for on-line solid-phase extraction, the above four estrogens in milk samples were concentrated and analyzed. The limits of detection for these estrogens were in the range of 1–8   ng   g −1 and reproducibility were less than 5.1% as RSDs ( n   =   6) with milk samples spiked at 100 and 1000   ng   g −1 of each analyte.