Simultaneous rapid structure identification and accurate quantitation of chiral drugs based on a home-built polarized Raman microscope

A chiral drug with different enantiomers exhibits different pharmacological activities. Structure identification, quality control, and accurate quantitation are all important issues for chiral drugs. So far, these concerns can be studied only by different techniques solely; one method that can investigate all the abovementioned issues simultaneously is needed. Such an approach can definitely promote the development of the drug industry. Raman spectroscopy has long been used for quantitation and has been utilized for chirality study in recent years, thanks to its molecular fingerprints and the optical activity of chiral molecules. In this study, we firstly investigate the polarization sensitivity of racemic ibuprofen and its (S)-enantiomer using our home-built polarized Raman microscope then successfully distinguish the racemic and its (S)-enantiomer by Raman optical activity (ROA) spectra and its principal component analysis (PCA) scatter plot. Notably, the combination of polarized Raman spectroscopy (PRS) and partial least squares regression (PLSR) is proposed to achieve accurate quantitation of commercial ibuprofens. The experimental results of the coefficients of determination (R²) are 0.957 for racemic ibuprofen and 0.988 for (S)-ibuprofen, and their root mean square error of prediction (RMSEP) values are 0.126% and 0.049%, respectively. These preliminary results give a hint that polarized Raman spectroscopy (PRS) is a powerful non-destructive analytical tool for drug applications. These preliminary results give a hint that polarized Raman spectroscopy (PRS) is a powerful non-destructive analytical tool for drug applications.