FOAM FLOTATION ENRICHMENT OF ENANTIOMERS

Adsorptive bubble separation methods are known to be useful for processing large amounts of material at a relatively low cost. These techniques have been used to enrich components from both heterogeneous and homogeneous solutions. There is a need for economical process-scale enantiomeric separations. Thus far there has been little evidence to support the feasibility of using an adsorptive bubble process to enrich enantiomers. We demonstrate that foam-forming chiral collectors can be used in conjunction with an inexpensive glass device to enantiomerically enrich some pharmaceutically important compounds as well as derivatized and underivatized amino acids. Factors that appeared to affect this waterbased separation include the following: (a) column length, (b) column geometry and packing, (c) gas now rate, (d) concentration of the collector and the racemate, (e) nature of the collector, (f) temperature, (g) pH, (h) reflux time, (i) foam dryness, and (j) the presence of other materials in the sample (e.g., miscible organic solvents, salts, etc.). The chiral collectors used in this study are known to be able to associate with analytes via ligand exchange interactions, hydrophobic inclusion complexation, and hydrogen-bonding interactions among others.