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Potentiometric measurements have been applied to the detection of enantiomeric separations on molecularly imprinted polymers. A flow-through column electrode, based on the use of polymers imprinted against L-phenylalanine anilide, is described. The electrode consisted of a glass column in which the polymer was packed and where the end frits constituted the electrodes. The flow stream potential across the column can be continuously recorded as solvent is pumped through the system. The column resolved the enantiomers of phenylalanine anilide as detected by both UV absorption and potentiometric measurements and the recorded signals could be correlated with the concentration of phenylalanine anilide. The calibration graphs obtained for the UV absorption of phenylalanine anilide were linear over the concentration range investigated, whereas the potentiometric signal was shown to be exponentially linear with concentration. The application of molecular imprints to the preparation of supports suitable for chromatographic separations of enantiomers and for the preparation of specific electrodes is discussed.

Molecular imprints were prepared utilizing only weak bonds between the print molecule and functional monomers; the bonding forces used in the imprinting process were only those weaker than covalent and ionic bonds. Methacrylate-based molecular imprints were prepared using a number of chiral compounds, including N-protected amino acid derivatives, as print molecules. Methacrylic acid was used as the functional monomer because the acid function of the monomer forms hydrogen bonds with a variety of polar functionalities, such as carboxylic acids, carbamates, heteroatoms and carboxylic esters, of the print molecule. Bulk polymers were prepared, ground and sieved to particles of size less than 25 microns, packed into high-performance liquid chromatographic (HPLC) columns and used for enantiomeric separations in the HPLC mode. The polymers were shown to effect efficient enantiomeric resolution of a racemate of the print molecule in addition to substrate selectivity for the print molecule in a mixture of substrates with very similar structures. For example, the enantiomers of Cbz-aspartic acid and Cbz-glutamic acid (Cbz = carbobenzoxy) were resolved with separation factors of 1.9 and 2.5, respectively, on polymers with molecular imprints of the L-form of the respective compounds. In addition, these polymers, prepared against Cbz-L-aspartic acid and Cbz-L-glutamic acid, respectively, had the ability to bind selectively the print molecule from a mixture of both racemates, although the two compounds differ only by one methylene group. The results presented represent a substantial widening of the scope of molecular imprinting in that it may now be possible to prepare molecular imprints against a very large number of compounds.