Universal enantioselective discrimination by Raman spectroscopy.

Distinguishing between the enantiomers of chiral substances and their quantification is an analytical challenge, in particular in the pharmaceutical and biochemical sectors. A Raman spectroscopic method for discrimination of enantiomers is proposed. Advantage is taken of the polarization properties when Raman scattering occurs in an optically active medium. It is shown that a conventional polarization-resolved Raman setup leads to identical spectra of the two enantiomers. However, inserting a half-wave retarder to rotate the signal polarization by a fixed angle enables the efficient and universal enantiomeric discrimination. Hence, the applicability of any polarization-resolved Raman experiment can be improved substantially without significant modification of the setup or the use of chiral labeling or the addition of a substrate for selective plasmonic enhancement. In principle, the proposed technique allows simultaneous speciation, enantiomeric discrimination, as well as structural and quantitative analysis.