Characterization of drug–cyclodextrin formulations using Raman mapping and multivariate curve resolution

Raman chemical imaging was used in the characterization of drug–excipient interactions between a drug and different types of cyclodextrins. Detailed analysis was carried out regarding the interactions between the active ingredient (API) and the cyclodextrins and the heterogeneity of the samples was studied using multivariate curve resolution–alternating least squares algorithm. The amount of recrystallized pure API was also estimated using the same curve resolution method. The Raman mapping results were validated via scanning electron microscopy–energy dispersive X-ray spectroscopy and X-ray powder diffraction. Raman mapping was found to be suitable to detect traces of pure crystalline API below the detection limit of X-ray powder diffraction.