Sensitive enantioseparation by transient trapping-cyclodextrin electrokinetic chromatography

An on-line sample preconcentration based on transient trapping was applied to cyclodextrin electrokinetic chromatography (CDEKC) to realize a highly sensitive chiral analysis in capillary electrophoresis. The partial introduction of a micellar solution before the electrokinetic injection of a sample solution provided the effective preconcentration and enantioseparation of chiral compounds, resulting in the up to 240-fold enhancements of peak intensity and 100-fold improvements of limit of detection of (R),(S)-1-aminoindan as the model analyte. The demonstrated method could be applied to the other pharmaceutical compounds, which allowed five chiral analytes to be resolved with 40- to 160-fold sensitivity enhancements at once. The enantioseparation efficiency of the proposed method was slightly lower as compared to the conventional CDEKC, while the acceptable baseline separations of enantiomers were obtained in transient trapping-CDEKC relative to the undesirable resolution in the CDEKC with other preconcentration techniques. Additionally, it was clarified that transient trapping-CDEKC was also applicable to the analysis of enantiomeric excess, providing the sensitive detection of 43 ppb of (R)-chlorpheniramine in 5 ppm (S)-chlorpheniramine solution commercially available.