SEPARATION OF AMINO-ACID ENANTIOMERS USING MICELLAR-ENHANCED ULTRAFILTRATION

Micellar-enhanced ultrafiltration (MEUF) is investigated as a large-sc ale technique for separating amino acid enantiomers. Specifically, L-5 -cholesterol glutamate, a chiral ligand-exchange cosurfactant, is used together with a nonionic surfactant to form mixed micelles that prefe rentially bind D-phenylalanine over L-phenylalanine in the presence of copper(II). Operational selectivities as high as 4.2 are obtained. Po tentiometric titrations using a water-soluble model compound similar t o the chiral cosurfactant indicate that the ternary copper complex wit h phenylalanine has a stereoselectivity for the D enantiomer which is significantly smaller than that observed in the MEUF system. Thus, the selectivity of the chiral ligand is sensitive to the ligand's local s olvent and structural environment. (C) 1994 John Wiley & Sons, Inc.