Study of the nature of recognition in molecularly imprinted polymers.

In the present study molecularly imprinted polymers (MIPs) were prepared against a series of structurally related compounds containing various numbers of pyridyl groups. The goal, to increase understanding of the mechanisms of recognition in MIPs, was achieved by comparing the patterns of retention of the imprinted compounds on the different MIPs when related to a blank (non-imprinted) polymer in a high performance liquid chromatography system. Furthermore, frontal analysis was carried out on three polymers: a blank, a pyridine-imprinted and a 4,4'-bipyridyl-imprinted polymer, to evaluate the number (Bt), average specificity and strength (dissociation constant; Kdiss) of the recognition sites. The Kdiss values of pyridine on the different polymers were in the range 0.10-0.12 M, and the amount of imprinted binding sites (Bt) 0.10-0.12 mmol/g. Kdiss values of 4,4'-bipyridyl were approximately 0.06 M, with Bt values equal to the above, except for in the anti-4,4'-bipyridyl polymer where the Kdiss was determined to be 0.02 M and Bt 0.07 mmol/g. From the results it can be concluded that multiple additive weak interactions dominate the recognition of the template molecules in these imprinted polymers.