HPLC determinations of enantiomeric ratios.
Evaporative light-scattering detection (ELSD) is widely applied in the HPLC analysis of organic compounds lacking a UV chromophore. However, this detection method is generally unsuitable for determination of enantiomeric ratios (er). The er calculated from a UV trace and an ELS trace of the same compound differs significantly. Because of the nonlinear concentration response of the ELS detector, a compound with an er of 95:5 appears to be enantiomerically pure by ELS detection. It is possible to obtain a calibration curve and to calculate a correction factor, but this procedure is time consuming and therefore not very practical for routine analyses. In contrast, a charged aerosol detector allows a very accurate determination of the enantiomeric ratios. Like the ELS detection, the CA detection is independent of the chromophore properties of the substrate. Therefore, we recommend the use of CA instead of ELS detection for determination of the enantiomeric ratios of non-UV active compounds.
Wipf
Peter
P
Center for Chemical Methodologies and Library Development (UPCMLD), University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA. pwipf@pitt.edu
Werner
Stefan
S
Twining
Leslie A
LA
Kendall
Christopher
C
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D008027:Light; D012542:Scattering, Radiation; D013237:Stereoisomerism