Delapril and manidipine characterization and purity evaluation in raw materials

Abstract

This study characterizes the solid-state of delapril hydrochloride (DEL) and manidipine dihydrochloride (MAN) raw materials using different analytical techniques. DEL (D1 and D2) and MAN (M1 and M2) were obtained from different suppliers and submitted to differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), Raman spectroscopy (RS), and scanning electron microscopy (SEM). For DEL, the TG/DTG analysis demonstrated three stage of mass loss between 140 and 402 °C. Different DSC curve profiles with melting points at 182.8 °C for D1 and 170.1 °C for D2 were verified. Moreover, incompatible results were also obtained in RS and SEM analysis for this drug. Nevertheless, when analyzed by liquid chromatography (LC), an additional peak was detected, demonstrating that the differences observed can be related to an impurity present in D2 sample and not to a possible polymorphism (as confirmed by XRPD). On the other hand, for MAN evaluation, all results were similar, showing that there were no differences between M1 and M2 samples. Besides the solid-state evaluation, the techniques employed in this study could also be used for quality control, stability studies, and for qualification of raw materials suppliers. Furthermore, for purity evaluations, complementary methods (such as DSC) can be useful, since there are impurities that don’t have UV/Vis absorbance, leading to absence of signal in LC–UV methodologies.