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Abstract:
Among the well known techniques for enantioseparation, lately the MIPs have been proven as an attractive way to obtain pure optically active components. MIPs prepared as HPLC monoliths (by "in situ" polymerisation) are of great interest concerning the simple way of preparation, low consumption of template and their use in a screening method for the best functional monomer for a given target molecule.
Several investigations were made concerning the ratio between porogen and monomers and the porogenic mixture1. The choice of the porogen is often determined by the solubility of the template. In the studies, that have been done so far, less attention was paid to the reactivities of different functional monomers. Since their reactivities are often different, the use of a certain monomer will have high impact on the monolithic structure.
The purpose of our work was the improvement of the monolithic structure of trimethylolpropane trimethacrylate (TRIM) MIPs with Toluene/Isooctane as porogenic mixture and different functional monomers: methacrylic acid (MAA), vinylimidazole (VI), acrylamide (AAM) and 4-vinylpyridine (4-VPy). Z-L-Phenylalanine (Z-L-Phe) was used as template and the enantioselectivity was determined by injecting racemic mixtures of Z-Phe.
Concerning the monolithic structure we found that the back pressure of the column increases by factor 10 when VI was used instead of MAA as functional monomer. VI is less reactive in this environment and will be consumed near the end of the polymerisation to give more compact monoliths. Nevertheless the VI monolith gave the better enantioseparation.
In order to improve the enantioseparation the investigation of the copolymer reactivity ratios in the porogenic mixture, the template/functional monomer ratios and the cross-linking ratio are intent to be examined.
1. C Viklund, et al. (1997), Preparation of Monoliths using Photoinitiated Polymerisation, Chem. Mater., 9, 463-471
