Ursodeoxycholic acid was amorphised by the processes of grinding, spray-drying and melt-quenching, and the physico-chemical properties of the amorphous samples were characterised Powder X-ray diffraction gave halo pattern, characteristcs of amourphous state, for all the samples. Since significant difference was observed on thermal analysis and solid-state NMR spectroscopy, however, the microscopic structure was considered to be different from each amourphous sample. From the comparison in the moisture sorption isotherm and surface area among the amorphous samples, it was concluded that water molecules not only adsorbed on the amorphous surface, but penetrated into the interior of the amorphous sampls. In order to estimate the energetics of sorption process, differential heat of sorption was calculated from water vapor sorption profiles determined at various temperatures through the Clausius-Clapeyron equation. Although different water vapor sorption isotherms were obtained for each amo
rphous sample, it is interestingly found that the profiles of different heat of sorption were almost the same among the three amorphous samples.
Sodium cromoglycate gave a gentle increase in water content against an increase of relative humidity on the water vapor sorption isotherm, and absorbs more than 20% of water by humidifying under 90% RH at 40ﾟC.By means of powderX-ray diffractometer equipped with a humidity-controlled sample chamber, three crystalline states were clearly distiguished by different hydration states. On the other hand, a new polymorph was obtaind by crystallinsation of sodium cromoglycate using 2-propanol as a poor solvent. This new crystals gave a step-wise water vapor sorption isotherm, and four crystal forms, at least, were found to exist corresponding to individual steps of the isotherm.
Moreover, remarkable results were obtained for moisture effects on crystallisation of amorphous drug, roles of moisture for drug adsorption on porous additives, water vapor sorption characteristics of ground sample of amino acid, effects of moisture on complexation of strictly linear amylose during the process of sealed-heating, etc. Less