Determining enantiomeric excess from overlapping HPLC peaks: discussion of errors in the methods

Enantiomeric excess can be determined from overlapping liquid chromatography peaks when a dual detector, e.g., UV/vis and circular dichroism (CD), is used. Two literature methods for the determination of the sensitivity factor, g, were analyzed and the errors involved in the calculation of the enantiomeric excess evaluated. It was shown that the most important part of the task is selecting the range of data used for the calculation of g. These data should be tested for autocorrelation and the data range reselected if the autocorrelation is high. The best results are obtained when both methods are used and the deconvolved curves obtained in each case fit completely to one another. Then the sensitivity factors, g, obtained by both methods are almost the same and the errors in the enantiomeric excess determination are minimized.