Preparation of doxycycline‐imprinted magnetic microspheres by inverse‐emulsion suspension polymerization for magnetic dispersion extraction of tetracyclines from milk samples

A magnetic dispersion extraction method was developed based on a molecularly imprinted magnetic microsphere ( MIMM ) for the selective clean‐up and enrichment of tetracycline antibiotics from milk samples. The MIMM s were prepared by inverse‐emulsion suspension polymerization, using doxycycline, trimethylolpropane trimethacrylate, acrylamide, methacrylic acid, and surface‐modified F e 3 O 4 as a template molecule, crosslinker, functional monomer, and magnetic component, respectively. Synthesis and extraction conditions were optimized for obtaining excellent affinity and high selectivity. The magnetism, covering amount, and selectivity of the magnetic microspheres were characterized by a vibrating sample magnetometer, thermogravimetric analysis, and a competitive recognition experiment. The MIMM s were applied to separate tetracycline antibiotics from milk samples by magnetic dispersion extraction, and an enrichment factor of 9.28 and a good sample clean‐up were obtained. The average recoveries of four tetracycline antibiotics were obtained in the range of 74.5–93.8% with a precision of 1.2–5.2%. The LOD s and LOQ s of the proposed method were in the range of 7.4–19.4 and 24.7–64.7 μg/kg, respectively. The results indicated that magnetic dispersion extraction using MIMM s is a powerful tool for food‐sample pretreatment with high selectivity and a simplified procedure.