Development of Electrophoretic Methods for Simultaneous Determination of Enantiomeric Ratio and Composition of Diastereomeric Salt Mixtures

Abstract

Obtaining enantiomeric pure compounds is—among other techniques—possible in a resolvation experiment via diastereomeric salt formation, excellently exemplified by a modified Pope–Peachy method performed in supercritical carbon dioxide as solvent. The salt precipitation is followed by supercritical fluid extraction (SFE) to separate the diastereomeric salts and the unreacted enantiomers. To evaluate the extraction efficiency, conversion and enantioselectivity achieved, it is essential to determine the enantiomer excess and the residual resolving agent content in extracts and raffinates. Carefully chosen experimental parameters enable the simultaneous determination of certain anions and cations in capillary electrophoresis in a single run, which has not been reported for diastereomeric mixtures so far. In this paper, a partially validated chiral selective cyclodextrin enabled capillary electrophoresis method is presented for the characterization of cis-permethrinic acid samples resolved with (R)-1-phenylethylamine prepared by the SFE-based resolvation technique. To evaluate the efficiency of the resolvation, a cyclodextrin enabled chiral separation method was developed applying permethylated-β-cyclodextrin as chiral selector. The theoretical possibility of the widespread application of the developed method (with minor adjustments) is justified for other selectands and selectors. The developed methods can be thereby applied for the fast and reliable control of resolvation experiments.