Development of a bimodal polarimetric response model for improved quantitation of enantiomeric mixtures under conditions of poor chromatographic resolution.

The combination of a chiral-selective separation mode with polarimetric detection was investigated in terms of its ability to quantitate enantiomeric mixtures of the dansylated derivatives of phenylalanine, threonine, and valine under conditions of poor chromatographic resolution. Using the difference between two Gaussian functions to model the bimodal response obtained using polarimetric detection and incomplete chiral resolution, correlation coefficients as high as 0.999 were obtained when actual enantiomeric fractions were plotted against observed enantiomeric fractions calculated from the fitting procedure.

Quantitative analysis of incomplete HPLC resolution of enantiomers. Fit of polarimetric detection for D- and L-phenylalanine to a gaussian function.

This report compares laser-based polarimetric and UV data for quantitating incompletely resolved enantiomers by HPLC. Using L- and D-phenylalanine as a working model, response data is shown across the entire detection region while emphasizing the regions at or near 100% L, 100% D and 50:50 L:D at resolutions between 0.4 and 1.

Determination of enantiomeric excess using a chiral selective separation mode and polarimetric detection.

The quantitative capabilities of a system that combines a chiral selective separation mode with polarimetric detection (CSS/PD) were investigated 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 mudeg 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 were measured as analytical descriptors of the bimodal response function of this polarimetric detector.