Preparation of molecularly imprinted polymers based on core-shell magnetic mesoporous silica and application in the determination of estradiol.

A selective adsorbent was fabricated and evaluated for its applicability to trace E2 analysis by grafting a molecularly imprinted polymeric shell onto a magnetic nanoparticle encased in a mesoporous SiO2 layer (denoted Fe3O4@mSiO2@MIP) with E2 as the imprinting template. The morphology and microstructure of the resulting Fe3O4@mSiO2@MIP were characterized by scanning electron microscopy and transmission electron microscopy, and its functional groups were determined by Fourier-transform infrared spectroscopy. Its adsorption performance was investigated through kinetic, thermodynamic, and selectivity studies, and relevant models were adopted to interpret the adsorption mechanism. Adsorption followed pseudo-second-order kinetics and was well described by the Freundlich isotherm, yielding a capacity of 4.01 mg g-1 within 30 min together with a notable imprinting factor (2.36). Compared with the control non-imprinted material (Fe3O4@mSiO2@NIP), the imprinted sorbent (Fe3O4@mSiO2@MIP) exhibited markedly enhanced adsorption toward E2. Under the optimized magnetic solid-phase extraction (MSPE) conditions, an MSPE-HPLC-UV method was established for determining E2 residues in egg and milk samples. The method achieved an enrichment factor of 36 with satisfactory recoveries ranging from 86.7% to 101.2%. Furthermore, the prepared Fe3O4@mSiO2@MIP could be regenerated and reused for at least seven cycles, confirming its feasibility for practical use.