Preparation of Novel Restricted Access Material-Surface Molecularly Imprinted Polymers via Reversible Addition-Fragmentation Chain Transfer Polymerization for 17β-Estradiol Determination in Milk Powder

Novel surface molecularly imprinted polymers ( MIPs ) combined to restricted access materials ( RAMs ) were prepared by reversible addition-fragmentation chain transfer ( RAFT ) polymerization for selective and efficient determination of 17β-estradiol ( E2 ) in milk powder. TiO 2 nanoparticles were coated by a MIP layer via RAFT polymerization and formed a core-shell structure. 3-Glycidoxypropyltrimethoxysilane was grafted on the surface of MIP and hydrolyzed to form hydroxyl group to block unspecific adsorption of macromolecules. RAM-MIPs were characterized by infrared, thermal analyzer, surface area and porosimeter analyzer, and others. RAM-MIP exhibited efficient adsorption performance for E2. E2 in milk powder was dissolved in water, cleaned up by RAM-MIP solid phase extraction cartridge, silanized by N-methyl-N-(trimethylsilyl)trifluoroacetamide, dithioerythritol, and trimethyliodosilane, and determined by gas chromatography-mass spectrometry. The limit of quantification for E2 in milk powder samples was 0.001 mg/kg. The recoveries and relative standard deviations of E2 spiked at 0.001–0.01 mg/kg were 82.0–107.5% and 2.9–5.8%, respectively. Thus, RAM-MIP can be successfully applied to the determination of E2 in milk powder samples.