Use of single-isomer, multiply charged chiral resolving agents for the continuous, preparative-scale electrophoretic separation of enantiomers based on the principle of equal-but-opposite analyte mobilities

Abstract

A novel approach to continuous, preparative-scale electrophoretic enantiomer separations has been developed based on the observation that stable, equal-but-opposite effective mobilities can be created for the enantiomers of a single-charged analyte by complexing them with a single- isomer, multiply charged resolving agent, provided that the charge of the resolving agent is opposite in sign to that of the uncomplexed analyte enantiomers. When such an analyte-resolving agent system is fed into a continuous, free-flow electrophoretic apparatus, stable, steady-state operating conditions can be established which permit the continuous feeding of the racemic analyte and the collection of pure enantiomers at the opposite sides of the feed stream. This concept is demonstrated via the separation of the enantiomers of terbutaline using heptakis-6-sulfato-β-cyclodextrin as resolving agent, affording production rates as high as 2.8 mg/h in the general-purpose, continuous free-flow electrophoretic system, the Octopus.