Physico-chemical properties and isothermal transition of acetazolamide polymorphs.

A Novel Method for Estimation of Transition Temperature for Polymorphic Pairs in Pharmaceuticals Using Heat of Solution and Solubility Data.

“…2) were identical to those reported previously. 9,10,16,17) The results of TG and HPLC suggested that each of the polymorphs was not solvated and did not decompose.…”

“…These dissolving solvents were chosen to correspond with those used in previous studies. [9][10][11][12] The plots in Fig. 3 show the concentrations attained in solution for each polymorphic pair as a function of time in the presence of an excess of the solid phase.…”

“…Indomethacin Polymorphs: Form a was prepared by the method of Kaneniwa 10) as follows. Ten grams of indomethacin was dissolved in 10 ml of ethanol at 80°C; the undissolved indomethacin was filtered off; and 20 ml of distilled water at room temperature was added to the indomethacin-saturated ethanol solution at 80°C.…”

“…In previous studies, [9][10][11][12][13][14][15] this equation has been widely applied for the estimation of transition temperature for the enantiotropic polymorphic pairs. At a temperature of T 1 , the logarithmic solubilities of Form A and B in a polymorphic pair are written as Eqs.…”

“…For these reasons, a number of studies on the estimation of transition temperature have been reported until now. [9][10][11][12][13][14][15] In these studies, transition temperature has been estimated by linear extrapolation of van't Hoff plots (logarithmic solubility versus reciprocal of absolute temperature plots) for each polymorph; the temperature at which these extrapolated lines intersect is the transition temperature.…”