Separation of mixtures of chiral volatile anestethics via modified porous glasses

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The separation of racemic mixture of fluranes applied as anaesthetic gases is of large interest, since the specific effects of the individual enantiomers is not sufficiently known. Corresponding investigations are still hampered due to the limited availability of the corresponding pure enantiomers.In the first period of this project glass beads of various pore and particle sizes were synthesized. It was possible to immobilize suitable cyclodextrin-based selectors on the surface of these beads and to perform first successful enantioseparations.In the currently ongoing funding period the synthesis of the supports has been improved further. Glass beads in which the pore structure was altered by pseudomorphic transformation were synthesized exhibiting already functionalized surfaces. The synthesis was reproducible and larger amounts of samples could be provided for chromatographic investigations. In comparison to the pathway used in the first period, the fixation of the enantioselective selector could be further improved allowing for better separation results. A more detailed characterization regarding the intraparticle mass transport of chiral molecules was performed exploiting IR micro-imaging. Adsorption capacities and separation factors were determined analyzing results of chromatographic column overloading experiments. A simplified mathematical model, which is capable to describe and optimize the chromatographic columns filled with the prepared particles, was developed and applied to estimate the productivity of the separation for columns with larger diameters.The production of pure enantiomers is in the focus of the third funding period. Larger column dimensions and an improved experimental set-up should be used. The enantiomers leaving the separation column should be subsequently captured in an adsorber before desorbing and condensing them. It is further planned to test the applicability of the model developed with respect to predict the separation process occurring in larger columns over a wider parameter range. An anticipated extension of the model will be realized by incorporating available transport parameters. In addition, it is planned in the third period to perform orienting small scale experiments with new particles of larger diameter and with core-shell-particles. These new supports are potentially advantageous for later separations in an even larger scale.