A novel core–shell magnetic nano-sorbent with surface molecularly imprinted polymer coating for the selective solid phase extraction of dimetridazole

A novel core–shell magnetic nano-sorbent with surface molecularly-imprinted polymer coating was prepared via a sol–gel process. Methyltrimethoxysilane and 3-aminopropyltriethoxysilane were used as functional monomers, tetraethyl orthosilicate as cross-linker, and Al3+ as dopant to generate Lewis acid sites in the silica matrix for the metal coordinate interactions with the template dimetridazole (DMZ). The ratios of the monomers, the dopant, and the cross-linker, were optimised by a OA9 (34) orthogonal array design. The resultant sorbent was characterised by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, and magnetometry. The binding performances of the sorbent were evaluated by static, kinetic and selective adsorption experiments. The nano-sorbent was successfully applied to solid phase extraction followed by spectrophotometric determination of DMZ in real samples. Spiked recoveries ranged from 90.33% to 106.20% for egg, milk powder, and pig feed samples, with relative standard deviations of less than 4.54%.