Solid-state study of Captopril and Metoprolol Tartrate binary system

The structural and thermal characterization of Captopril (CA) and Metoprolol Tartrate (MT) pure com- pounds and binary system have been obtained. Solid–liquid equilibrium for binary mixture CA–MT was investigated using differential scanning calorimetry. Simple eutectic behavior for this system was observed. The experimental solid–liquid phase temperatures were compared with pre- dictions obtained from available eutectic equilibrium models. The results indicate non-ideality in this mixture. The negative value of the mixing enthalpy indicates the presence of clusters with hydrogen bonds formation in the melt, as confirmed by FT-IR measurements. The prepara- tion of ground mixtures demonstrated that the application of mechanical energy can result in the partial melting of the sample because of the eutectic behavior. Trans–cis iso- merization of CA was observed for the samples annealed at high temperature, anticipated due to the presence of MT in the system.