Chiral capillary electrophoresis: Facts and fiction on the reproducibility of resolution with randomly substituted cyclodextrins


Schmitt U., Ertan M., Holzgrabe U.

ELECTROPHORESIS, vol.25, no.16, pp.2801-2807, 2004 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 25 Issue: 16
  • Publication Date: 2004
  • Doi Number: 10.1002/elps.200405932
  • Title of Journal : ELECTROPHORESIS
  • Page Numbers: pp.2801-2807

Abstract

Comparative enantioseparation of the enantiomers of 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate was performed with cyclodextrin (CD)-modified capillary electrophoresis (CE). Two single isomers, beta-CD, heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD), and heptakis(2,6-di-O-methyl)-beta-CD (DM-beta-CD) of 98% purity as well as heptakis(2,3-di-O-acetyl)-beta-CD were used and compared in terms of resolution power to randomly methylated and corresponding acetylated beta-CDs, which were synthesized in our laboratory. The methylated ones were characterized by means of matrix-assisted laser desorption/ionization-time of flight-(MALDI-TOF) mass spectrometry. By testing defined mixtures of single isomers and comparing their resolution power to randomly substituted CDs of similar degree of substitution we could show, that a simple characterization by the average molecular degree of substitution (DS) is not sufficient. In order to get reproducible results, a clearly defined substitution pattern is necessary, which is not given using randomly substituted CDs. Taken together, a validation of a chiral separation with "undefined" CD derivatives is almost impossible.