Chiroptical detectors for the study of unusual phenomena in chiral chromatography

Differentiation of enantiomers in chromatography requires specific detectors, based on polarimetry or circular dichroism. Their use is limited to chiral HPLC and SFC. We explain the operating principles of the different chiroptical detectors available and stress the influence of working wavelength and mobile phase on the output signal. Current and relevant applications of chiroptical detectors are absolute configuration assignment, measurement of enantiomeric excesses in complex mixtures and determination of elution order. We focus on the reversals of enantiomeric elution order, an important subject for the understanding of the chiral recognition mechanisms. We review the main parameters which can induce a reversal, show the usefulness of chiroptical detectors to easily identify reversals and emphasize the significance of the isoenantioselective temperature. The aim of this chapter is to highlight the valuable information provided by chiroptical detectors to study unusual behaviour in chiral HPLC and SFC, reversals of enantiomeric elution order and exchange phenomena as dynamic chromatography and self-disproportionation on achiral columns.