Layer-by-layer fabrication of restricted access media-molecularly imprinted magnetic microspheres for magnetic dispersion microextraction of bisphenol A from milk samples

A novel restricted access media-molecularly imprinted magnetic microsphere (RAM-MIMM) was prepared through layer by layer modification. The magnetic nanoparticles were coated with silica gel, modified with the amino group, coated by BPA-imprinted sol-gel film and grafted with the epoxy silane coupling agent. The RAM-MIMMs were characterized by SEM, TEM, FT-IR and adsorption experiments. The RAM-MIMMs were prepared with the average diameters of around 300 nm and the coating thickness in the range of 10-15 nm, and exhibited high selectivity (2.54) of the imprinted cavities and hydrophilicity of the external surface with water compatibility and exclusion biomacromolecules. The RAM-MIMMs were used for magnetic dispersion microextraction of BPA from milk samples. The average recoveries were obtained in the range of 85.2-98.6% with a precision of 2.2-4.6%. The limits of detection and quantitation of the proposed method were in the range of 4.70-10.51 mu g kg(-1) and 15.65-35.02 mu g kg(-1), respectively.