Vanillin-molecularly targeted extraction of stir bar based on magnetic field induced self-assembly of multifunctional Fe3O4@Polyaniline nanoparticles for detection of vanilla-flavor enhancers in infant milk powders

•Fe3O4@PANI NPs were firstly applied into the preparation of MIPs-SB.•A magnetic field-induced self-assembly coating was formed by one-step.•The MIPs coating presented higher adsorption capacity and faster dynamics.•The coating was used for selective extraction of flavor enhancers in milk powders.

A molecularly imprinted stir bar was constructed based on Fe3O4@Polyaniline nanoparticles with magnetic field-induced self-assembly process. The monomer, methacrylic acid, was pre-assembled into the pre-polymers with vanillin as template by the formation of hydrogen bonds. After that, the magnetic complexes were generated by the hydrogen bonding, the hydrophobic and π–π interaction between the pre-polymers and Fe3O4@Polyaniline. The complexes were adsorbed on the surface of magnetic stir bar under the magnetic induction, and the coating of vanillin-molecularly imprinted polymers was generated by the one-step copolymerization basing on the cross linking of ethylene glycol dimethacrylate. The molecular imprinting stir bar showed superior selectivity and fast binding kinetics for vanillin, and was used for the enrichment of vanilla-flavor enhancers (vanillin, ethyl maltol and methyl vanillin) in infant milk powders. The results measured by HPLC-UV exhibited good linear ranges of 0.01–100, 0.02–100 and 0.03–100 μg mL−1 with the limit of detection of 2.5–10.0 ng mL−1, and the recoveries were 94.7–98.9%, 82.1–96.7% and 84.5–93.2% with RSD < 7.2% for the three enhancers, respectively.

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