Synthesis and characterization of the core-shell magnetic molecularly imprinted polymers (Fe ₃O ₄@MIPs) adsorbents for effective extraction and determination of sulfonamides in the poultry feed

In this study, we present a general method to prepare the core-shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs) for sulfamethazine (SMZ). The resulting Fe ₃O ₄@MIPs NPs possess a highly improved imprinting effect, fast adsorption kinetics and high adsorption capacity, and can be applied to extract sulfonamide in the poultry feed. In this protocol, the magnetite NPs were synthesized by co-precipitating Fe ²⁺ and Fe ³⁺ in an ammonia solution first. Silica was then coated on the Fe ₃O ₄ NPs using a sol-gel method to obtain silica shell magnetic NPs. Subsequently, the vinyl groups were grated onto silica-modified Fe ₃O ₄ surface by 3-methacryloyloxypropyltrimethoxysilane. Finally, the MIPs films were formed on the surface of Fe ₃O ₄@SiO ₂ by the copolymerization of vinyl end groups with functional monomer, methacrylic acid, cross-linking agent, ethylene glycol dimethacrylate, the initiator azo-bis-isobutyronitrile and template molecule, sulfamethazine. The morphology, magnetic, adsorption and recognition properties of Fe ₃O ₄@MIPs NPs were characterized using transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transform infrared (FT-IR) spectrometer, vibrating sample magnetometer (VSM) and re-binding experiments. The results showed that the binding sites of Fe ₃O ₄@MIPs were good accessibility, fast adsorption rate and the maximum adsorption capacity of Fe ₃O ₄@MIPs to SMZ was 344.8μgg ^-1. The selectivity of the obtained Fe ₃O ₄@MIPs NPs were elucidated by the different rebinding capability of SMZ and structural related sulfonamides in the mixed solution. The results indicated that the Fe ₃O ₄@MIPs had high imprinting factor 9.5 and significant selectivity. A method was developed for enrichment and determination of SMZ in the poultry feed samples with recoveries of duck and chicken feed ranging from 63.3 to 76.5% and 68.7 to 74.7%, respectively and the relative standard deviations (RSD) (<6.7%).