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Abstract: Tyrosine-imprinted microspheres have been prepared in an aqueous system by seed swelling and suspension polymerization, using trimethylolpropane trimethacrylate (TRIM), acrylamide (AM) as well as methacrylic acid (MAA), linear polystyrene and toluene as crosslinker, functional monomers, seeds and porogens, respectively. The size distribution proved to be greatly influenced by the ratio of water:TRIM (W/T) and the concentration of dispersant. When W/T was 46:1 (v/v), 4.6% (by mass) of poly(vinyl alcohol) (PVA) was used as dispersant, the molar ratios of tyrosine, MAA, AM and TRIM were 1:8:8:17, the polymer beads had the better size monodispersity, and the average size was 135mum, while the sizes of the pores on the beads surfaces ranged from 1.25mum to 9.01mum. The adsorption behaviour and molecular selectivity of the beads were analysed using liquid chromatography; the results showed that the adsorption behaviour of the beads followed the rule of Langmuir, and the value of saturated absorption was 0.197 mmol g(-1). The tyrosine-imprinted polymers exhibited an inherent selectivity for tyrosine; when phenylalanine was used as the competing molecule the separation factor a was up to 1.91. However, the control polymers did not have this special molecule-selection capability, and the relative separation factor beta was about 1.82 compared with the imprinted polymers. (C) 2002 Society of Chemical Industry