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Molecular imprinting technology can be used to generate specific artificial polymeric receptors, i.e., high affinity stationary phases, as already shown for peptides and many other food ingredients. In this work, polymers have been molecularly imprinted with three exemplary antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and propyl gallate (PG). Results of chromatographic evaluations are presented, demonstrating the specificity of the imprinted polymers (MIP) compared to non-specific control polymers (CP). For a BHA imprinted polymer and the respective analyte BHA a separation factor of α=kBHA-MIP′/kCP′=1.12 was found, whereas for the BHT-MIP a higher selectivity was determined with α=kBHT-MIP′/kCP′=1.47. Using the PG selective MIP for PG as analyte a value of α=kPG-MIP′/kCP′=1.24 could be achieved. Furthermore, results of extraction procedures based on MIP and CP phases are presented, demonstrating for instance a higher selectivity of the BHA-MIP in comparison with its CP when using methanol or acetonitrile as analyte solvent, and of the PG-MIP when performing the extraction in acetonitrile.

Enzymes play an important role as highly specific catalysts in biotechnology [J. Biotechnol. 66 (1998) 3; Hydrolases in Organic Synthesis, Wiley, New York, 1999] as well as in chemical reaction engineering [J. Biotechnol. 59 (1997) 11; Trends Biotechnol. 13 (7) (1995) 253]. However, the drawbacks of these biomaterials are poor durability and relatively high costs of production. Thus, the technique of molecular imprinting [Bio/Technology 14 (1996) 163; Angew. Chem. Int. Ed. Engl. 34 (1995) 1812; Anal. Commun. 36 (9) (1999) 327; J. Chromatogr. 781 (1997) 43] can be applied for generating much more stable polymeric mimics of biological enzymes. For this purpose, a stable transition state analogue (TSA) of a selected reaction must be chosen as template [Macromol. Rapid Commun. 19 (1998) 671; Curr. Opin. Chem. Biol. 3 (1999) 759]. The imprint of the TSA acts like a catalytically active centre. This binding site shows its catalytic effect by reducing the activation energy of the specific reaction. In the work presented here, molecularly imprinted catalytically active polymers have been generated and investigated in chemical reaction engineering processes, using batch reactors and continuously driven reactors equipped with these polymers. Parameters such as temperature, concentration of substrate or volume flow have been varied, reaction rates measured and kinetic data recorded. Based on this information, the rate constants of the reaction have been calculated, as well as the relative catalytic effects. It is demonstrated that imprinted polymer catalysts show obvious catalytic properties and can be used as an alternative for traditional catalyst materials.