Methodology for assessing the properties of molecular imprinted polymers for solid phase extraction
Four molecular imprinted polymers (MIPs) were prepared using propranolol as template molecule. The retention and recovery of propranolol and eleven structurally related compounds were assessed on all four MIPs and a blank polymer in solid phase extraction (SPE) experiments using methanol–water–triethylamine (TEA) (1%) elution solvents. Cumulative elution curves were produced and these were compared between blank and imprinted polymer for each compound. Only one polymer demonstrated significantly different retention properties compared to the blank indicating that only this polymer was sufficiently selective to be considered for SPE. In the case of the selective MIP, two classes of compounds were observed, with one group demonstrating selective retention whilst the second group showed similar retention on both MIP and blank. The compounds showing selective retention on the MIP were closely structurally related to the template propranolol, differing in having methoxy substituents on the naphthyl or a modified alkyl side chain whilst those that were equally well retained on the blank and MIP all contained amide groups close to the secondary amino group on the side chain. The use of eleven structurally related compounds in this way enabled the key structural features important to specific binding to the molecular imprints to be explored. They also provide a means to rapidly evaluate the polymers in order to select those suitable for SPE from aqueous solutions.