Prediction and experimental determination of the binary and ternary phase diagrams of (±)medetomidine hydrochloride

The binary phase diagram of medetomidine hydrochloride was determined based on thermogravimetric differential thermal (TGA/DTA) measurements. The binary phase diagram presented a eutectic point in the 19:81 [(R)/(S)] composition and the ternary phase diagram in the presence of 2-propanol showed a eutectic point in the 75:25 [(S)/(R)] composition, both characterizing the product as a racemic compound forming system. The solubility of enantiomeric mixtures in 2-propanol was measured at 10, 20 and 30 °C. The ideal solubility curves of the mixtures were calculated and the activity coefficients derived. A semi-empirical thermodynamic model UNIversal QUAsi-Chemical (UNIQUAC) was used to predict the solubility of various compositions of enantiomers at different temperatures. There was good agreement between the experimental solubility data of medetomidine hydrochloride and the results obtained from the UNIQUAC equation.

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