Chiroptical detection during liquid chromatography: Deconvolution of overlapping peaks of enantiomers and its...

The peaks of enantiomers in liquid chromatography (LC) frequently overlap for different reasons. The experimental curve can be deconvolved, i.e., transformed into the two curves of the enantiomers, without any assumption concerning their peak shapes. Besides the usual photometric UV detection, resulting in absorbance A, polarimetric or circular dichroic detection is required, providing the rotation 90 degree angle alpha or the differential absorbance DeltaA, respectively. The accuracy of the ratio alpha/A or DeltaA/A for the pure enantiomers is essential for the quality of the deconvolution. The determination of these ratios, using the overlapping peaks, and the subsequent computer deconvolution of the latter are discussed in more detail than in the earlier publications, e.g. Ref. 1 concerning this particular method. The computer program developed for this purpose is characterized. A condition is given which limits the availability of ratios and, therefore, the possibility of deconvolution. Several novel examples are described which stem from the following fields of application of deconvolved peaks: actual optical purities during LC (on-line analysis), overall optical purity of a sample, purities of chromatographic peaks, and, finally, enantiomerization during LC.