Preparation of Warfarin Molecularly Imprinted Polymer and Analysis on Its Adsorbility

Warfarin (WFR) molecularly imprinted polymer (MIP) was prepared by suspension polymerization using WFR as template. Mole ratio of WFR and other two reactantsi.e. the functional monomer glycidyl methacrylate (GMA) and the cross-linking agent divinylbenzene (DVB), as optimized by orthogonal test, was found to be WFR:GMA:DVB=1:5:60. In the synthesis, WFR was firstly sonicated with GMA in CHCl₃ (15 mL) for 5 min to give a pre-polymer. And then 0.17 g of 2% (propotion of mass sum of the monomers and the cross linker) initiator dibenzoyl peroxide chloro form solution together with DVB 8.499 mL were added to the reaction mixture and sonicated again for 20 min. After which, the mixture was added dropwise to 100 mL of 10 g·L^-1 polyvinyl alcohol (PVA) solution, and at the end of the dropwise-addition, the mixture was reacted at 80℃ for 8 h to give the required polymer. The supernatant was separated and discarded. The precipitate was washed repeatedly with boiling water until clear and transparent washings was obtained to remove PVA on its surface, and the solid showed a appearance of slight yellow colored micro-globular particles. The MIP was separated and dried at 60℃. The dried MIP was then washed by refluxing in soxhlet's extractor with 150 mL of a mixed solvent of methanol and acetic acid with a volume ratio of 4:1, to remove WFR and finally washed with methanol to eliminate residual acetic acid. The washed MIP was again dried at 60℃ to give the final product. Non-molecularly imprinted polymer (NIP) was prepared in the same way but without addition of WFR. It was shown by the SEM image that the MIP displayed a state of even micro-globular particles without any damage on their surfaces, but with micro-pores on the surfaces providing the possibility of good adsorbility. As shown by the results of test for its adsorption efficiency, amounts of WFR adsorbed by MIP and NIP were all increased with the increase of mass concentrations of WFR, and adsorption equilibrium was achieved when WFR attained to 20 mg·L^-1. Amounts of WFR adsorbed by MIP were higher than those by NIP at all mass concentrations. It was shown by the isotherm, that the adsorption was consistent with the Langmuir mode and belonged to single-molucular layer adsorption, and as shown by the result of the preudo-2nd order kinetic equation, the adsorption was the result of chemical interaction. Test for adsorbility of MIP and NIP towards WFR and 2 other compounds having part of their functional groups similar to that of WFR was made, giving results showing higher selectivity for MIP as compared with NIP.