Effect of the temperature on a hydrate diclofenac salt

The salt Diclofenac/N-(2-hydroxyethyl) pyrrolidine when crystallizes from w ater forms a di-hydrate, which looses the crystallization water molecules o n heating or in the presence of silica gel, undergoing a phase transition. The two processes were followed at room temperature, at 40 and 50 degrees C by thermal analysis and analyzing the dimensional parameters obtained by s canning electron microscopy as a function of the changes occurring in the s olid state. The fractal dimension of the particle surface (D-S) was determi ned for the di-hydrate, the anhydrate and the anhydrous forms: D-S values a re close together suggesting that the processes modify only slightly the ex ternal morphology of the particles. The reactive dimension (D-R) to dissolu tion suggests that the salt after the thermal treatment has a dissolution b ehaviour identical to that observed for the salt obtained from organic solv ents. The two processes de-hydration and phase transition can be carried ou t at relatively low temperature, suggesting an important pathway to obtain the anhydrous form starting from the di-hydrate one. (C) 1999 Elsevier Scie nce B.V. All rights reserved.