Thermal and Spectral Characterization of a Binary Mixture of Medazepam and Citric Acid: Eutectic Reaction and Solubility Studies

Abstract

Medazepam, citric acid and their binary mixtures were studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) for thermal and structural properties. The DSC data show a simple eutectic peak at 370 K. To determine the exact mole fraction at which the eutectic occurs, Tamman’s triangle was used. The obtained results show that the eutectic mixture appears at a molar fraction of medazepam of approximately 0.85. The excess thermodynamic functions GE, SE and μE were calculated, and the results were interpreted to evaluate the interactions that occur between the components of the mixture. The FTIR results were used to confirm the eutectic formation. Solubility tests in deionized water show a 40-times increase in the medazepam solubility from the eutectic mixture, from 0.73 μg/mL to 28.61 μg/mL. However, further tests showed that the acidic character of the sample was the main factor responsible for this increase.