Journal of Chemical Thermodynamics, Vol.138, 297-303, 2019
The dissolution behaviour and apparent thermodynamic analysis of diprophylline in pure and mixed solvents
Co-solvent plays an important role in drug crystallization. More importantly, the change of temperature and the addition of co-solvent can make the operation of crystallization purification more controllable. In this work, the solubility of diprophylline in methanol, ethanol, n-propanol, isopropanol, acetone, acetonitrile, ethyl acetate, 1,4-dioxane, water, toluene and mixture of (methanol + water) was experimentally determined at T = 283.15-323.15 K. The solubility data obtained experimentally in all studied pure solvents followed the sequence: water > 1,4-dioxane > methanol > acetonitrile > isopropanol > ethanol > n-propanol > ethyl acetate > toluene > acetone. In addition, in mixture of (methanol + water) the solubility increases at first and then decreases with the increasing mass fraction of methanol. The composition dependence of the solubility has a maximum around (methanol mass fraction) w = 0.4 at all investigated temperatures. Moreover, the effect of solvent properties on solubility is briefly discussed. The modified Apelblat equation, lambda h equation, Jouyban-Acree model and CNIBS/R-K model are applied to correlate the solubility. All the values of RAD and RMSD are no more than 5.34 x 10(-2) and 5.83 x 10(-4), respectively. Apparent thermodynamic analysis indicates that the dissolution is an endothermic and entropy driven process. (C) 2019 Published by Elsevier Ltd.