Well-defined sulfamethazine-imprinted magnetic nanoparticles via surface-initiated atom transfer radical polymerization for highly selective enrichment of sulfonamides in food samples

Abstract

In this work, a novel kind of core–shell magnetic molecularly imprinted polymer (MIP) for sulfamethazine (SMZ) was synthesized by the surface-initiated atom transfer radical polymerization (ATRP) strategy. In this protocol, polydopamine was formed on the Fe₃O₄ nanoparticles (NPs) in 10 mM Tris–HCl buffer solution (pH 8.5). The initiator bromide reagent of ATRP was then grafted onto the polydopamine surface. Finally, the MIP layer was formed on the surface of Fe₃O₄ by the copolymerization of sulfamethazine as a template, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking agent using an organometallic catalyst comprising Cu(I)Br and pentamethyldiethylenetriamine. The morphology and magnetic, adsorption and recognition properties of Fe₃O₄@SMZ-MIP NPs were characterized using transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometry (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and re-binding experiments. The controllable nature of ATRP allows the growth of a uniform MIP layer with adjustable thickness, providing a large adsorption capacity (680.27 μg g⁻¹), fast kinetics about 40 min to equilibrium, and a considerably high imprinting factor of 17.02. The feasibility of the enrichment of sulfonamides by Fe₃O₄@SMZ-MIP was demonstrated using egg samples spiked with SMZ and SMR. The recoveries of SMZ and SMR ranged from 76.7 to 93.0% and 69.3 to 77.2%, respectively, and the relative standard deviations (RSD) were <7.0%. In addition, Fe₃O₄@SMZ-MIP showed good reusability for at least five repeated cycles.