Retentivity and enantioselectivity of uniformly-sized molecularly imprinted polymers for (S)-nilvadipine in aqueous and non-aqueous mobile phases.

Uniformly-sized molecularly imprinted polymers (MIPs) for (S)-nilvadipine have been prepared by a multi-step swelling and polymerization method using methacrylic acid or 4-vinylpyridine (4-VPY) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linker, and toluene, chloroform, cyclohexanol or phenylacetonitrile as a porogen. The chiral recognition abilities of the MIPs for nilvadipine were evaluated using aqueous and non-aqueous mobile phases. Among the MIPs, the (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers prepared using toluene as a porogen showed the highest recognition ability for nilvadipine in both aqueous and non-aqueous mobile phases. In addition to molecular shape recognition, hydrogen-bonding interactions of the NH proton of nilvadipine with a pyridyl group of the (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers could play an important role in the retention and chiral recognition of nilvadipine in aqueous and non-aqueous mobile phases. Furthermore, the MIP for (S)-nilvadipine gave the highest molecular recognition ability when a porogenic solvent during polymerization was used as the mobile phase modifier.