Chromatographic resolution of the enantiomers of phenylpropanolamine by using molecularly imprinted polymer as the stationary phase

In this study molecular imprinting technology was employed to prepare a specific affinity sorbent for the resolution of phenylpropanolamine, a chiral drug. The molecularly imprinted polymer (MIP) was prepared by non-covalent molecular imprinting with either (−)- or (+)-phenylpropanolamine as the template. Methacrylic acid and ethylene glycol dimethacrylate were copolymerized in the presence of the template molecule. The bulk polymerization was carried out in chloroform with 2,2′-azobisisobutyronitrile as the initiator, at 4°C and under UV radiation. The resulting MIP was ground into powders, which were slurry packed into analytical columns. After removal of template molecules, the MIP-packed columns were found to be effective for the resolution of (±)-phenylpropanolamine racemates. The separation factor for the enantiomers ranged between 1.8 and 3.8 when the column was packed with MIP prepared with (+)-phenylpropanolamine as the template. A separation factor ranging from 2.1 to 3.6 could be achieved from the column packed with MIP, prepared with (−)-phenylpropanolamine as the template. Although the separation factor was higher with that previously obtained from reversed-phase column chromatography following derivatization with a chiral agent, elution peaks were broader due to the heterogeneity of binding sites on MIP particles and the possible non-specific interaction.