Preparation of molecularly imprinted polymers for warfarin and coumachlor by multi-step swelling and polymerization...

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF) and coumachlor (CC), MIP_WF and MIP_CC, respectively, were prepared using 4-vinylpyridine (4-VPY) as a functional monomer and ethylene glycole dimethacrylate (EDMA) as a crosslinker by multi-step swelling and polymerization. Six kinds of MIP_WF, MIP_WF1 - MIP_WF6, were prepared varying the concentrations of WF and 4-VPY, while maintaining the EDMA concentration constant, and their retention and molecular recognition properties were evaluated using a mixture of sodium phosphate buffer and acetonitrile as a mobile phase in LC. In addition to shape recognition, hydrogen bonding, ionic and hydrophobic interactions could affect the retention and molecular recognition of WF on MIP_WF, and ionic interactions seem to govern the retention and molecular recognition of WF above mobile phase pH 6 associated with higher molar ratio of 4-VPY to EDMA. Furthermore, MIP_CC was prepared under the same conditions with MIP_WF6, which gave the highest imprinting factor for WF. WF could be recognized more strongly on MIP_CC than MIP_WF6, and the imprinting factors of WF on MIP_WF6 and MIP_CC, respectively, are 2.68 and 5.03 using 20mM sodium phosphate buffer - acetonitrile (30/70, v/v)(final pH 6.1) as the mobile phase. This result indicates that the use of CC as a template molecule instead of WF could be useful for getting a higher imprinting factor for WF and for avoiding the leakage problem in the assay of WF in LC.