Our latest paper presents the study of simvastatin phase transitions with terahertz spectroscopy.
Simvastatin is an important pharmaceutical compound used for the treatment of hypercholesterolemia. It exhibits three polymorphic forms and they have been found to differ only by the rotational flexibility of the molecule's ester tail within the crystal. Our investigations have found that THz spectroscopy is sensitive to these subtle changes in rotational freedom and they are reflected in the baseline of the spectra. Essentially, the spectra are integrated responses of lattice vibrational features and rotational disorder. By tracking changes in the baseline with temperature, we are able to accurately determine the phase transition temperatures.
Nicholas Y. Tan and J. Axel Zeitler, Probing phase transitions in simvastatin with terahertz time-domain spectroscopy, Molecular Pharmaceutics, doi: 10.1021/mp500649q, ASAP.