MIXING CHROMATOGRAPHY AND SPECTROSCOPY TO ACHIEVE CHIRAL RECOGNITION WITH MOLECULAR MICELLES

 

ISIAH MANUEL WARNER

 

Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803

 

KEY WORDS: Separations, Chiral, Surfactants, Micelles, Polymeric Surfactants, Molecular Micelles, Fluorescence Anisotropy, Free Energy

 

ABSTRACT

 

Capillary Electrophoresis (CE) has become an important analytical tool for separation of charged analytes. This is because of the enhanced separation efficiency of the CE method for charged analytes. In addition, the CE method when used in combination with a micellar pseudostationary phase offers a number of advantages for separation of neutral analytes. This latter approach is called micellar electrokinetic chromatography (MEKC) and has been evolving with the use of other pseudostationary phases for the last two decades. In our laboratory, we have recently employed chiral polymeric surfactants(molecular micelles) for enhanced enantiomeric separations of racemic mixtures using MEKC. Our studies have shown that these polymers are usually more suitable than conventional micelles in MEKC. We have also sought to understand the factors which contribute to effective enantiomeric separation by use of chiral polymeric surfactants and in that regard, to develop better reagents. One of the methods that we have explored for probing chiral recognition, with great success, is fluorescence anisotropy (FA)(JACS 2001, 123, 3173-3174). We have demonstrated that FA directly correlates with our chromatographic measurements and that it is possible to extract the difference in free energy of interaction between two enantiomers by use of FA measurements. This talk will highlight some of our recent studies in the development of our chiral reagents and the use of FA to probe chiral recognition.