Abstract: The selective sorbents, oxacillin-imprinted microspheres, used in solid-phase extraction cartridge are needed to isolate the beta lactam antibiotics from samples. A method was developed to prepare these microspheres by precipitation polymerization, and the molecular recognition characteristics of these microspheres were studied. The optimized synthesis parameters were as follows. The amounts of template oxacillin, functional monomer acrylamide and crosslinker ethylene-dimethacrylate were 1, 4 and 20 mmol (molar ratio of 1∶4∶20); the solvent methanol was 100 mL, and initiator azodiisobutyronitrile was 5 mg. The polymerization was carried out at 60 ℃ for 24 h. There were two classes of binding sites in the oxacillin-imprinted microspheres. The dissociation constant of low affinity’s binding site was 10.846 mmol/L, and the max apparent binding capacity was 418.23 μmol/g. The dissociation constant of high affinity’s binding site was 2.627 mmol/L, and the max apparent binding capacity was 137.68 μmol/g. The adsorption quantity of the microspheres to penicillin-G, cefoperazone and cefazolin were 95%, 58% and 96% of that template. The molecularly imprinted polymers could be reused nine times without significant decrease on adsorption properties. The result of spiked milk sample proved that the oxacillin-imprinted microspheres could be directly used as the sorbents of solid phase extraction cartridge.

Key words: oxacillin, molecularly imprinted polymer, precipitation polymerization, beta lactam, solid-phase extraction