Phase Equilibria of the System Drug + Water

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The production and the application of pharmaceuticals customarily involve liquid solvents for reaction, separation, and formulation. In pharmaceuticals, poor water solubility and slow dissolution into the gastrointestinal tract are major obstacles for releasing new dosage forms into the market. These issues have been responsible for the rejection of 70 % of the potentially active drugs. In this experimental study devoted to the phase behavior of three binary systems made from drug (S-(+)-2-(4-(2-methylpropyl) phenyl) propanoic acid [ibuprofen], (2E,6E)-3,7,11-trimethyldodeca-2,6,10-trien-1-ol [farnesol], and ((R)-(6-methoxyquinolin-4-yl)((2S,4S,8(R)-8-vinylquinuclidin-2-yl)methanol [quinine]) and pure water. Beside the solubility in water (solid−liquid equilibrium, SLE), also the miscibility gaps (LLE) of two systems, namely (2E,6E)-3,7,11-trimethyldodeca-2,6,10-trien-1-ol + water and (S)-2-(4-(2-methylpropyl)phenyl)propanoic acid + water, were measured applying the equilibrium method in combination with different analytical methods, like Karl Fischer titration, HPLC, and UV−vis spectroscopy. From the solubility data, the heat of fusion of the studied drugs could be extracted. An important factor which can have a significant impact on the thermodynamic data is the type of the investigated isomer.