DETERMINATION OF ENANTIOMERIC EXCESS USING A CHIRAL SELECTIVE SEPARATION MODE AND POLARIMETRIC DETECTION

The quantitative capabilities of a system that combines a chiral selec tive separation mode with polarimetric detection (CSS/PD) were investi gated in terms of the ability to quantitate enantiomeric mixtures even under conditions of poor chromatographic resolution. The laser-based polarimetric detection system can provide a rotational sensitivity on the order of 10 mu gdeg corresponding to a minimum measurable quantity of 10 ng for a compound with a specific rotation of 100 deg (g/ml)(-1 ) dm(-1). For the chromatographic studies, peak height and peak area w ere measured as analytical descriptors of the bimodal response functio n of this polarimetric detector. Analyses of the dansylated enantiomer s of the amino acids phenylalanine, threonine, and valine have shown t hat chromatographic resolution and specific rotation are important fac tors affecting the shape of the polarimetric response curve. With CSS/ PD, enantiomeric materials can be quantitated at both low and high ena ntiomeric excess (ee) even at resolutions of 0.3-0.4. (C) 1997 Elsevie r Science B.V.