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

Abstract

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 1.4. In general, the poorer the resolution, the greater the improvement in detectability with the polarimeter when compared to UV detection. This is due to the inherent bipolar nature of the polarimetric signal, which creates a well-defined crossing point for integration of an enantiomeric pair. In our previous work, we described the improvement in measurement precision when applying a bipolar gaussian peak model to the raw chromatographic peak data. This study will measure the model's effect on improving accuracy. This study should be applicable to other chiroptical detection strategies that produce a bipolar signal for enantiomers, such as circular dichroism and circularly polarized luminescence.