Determination of hydrate transition temperature using transformation kinetics obtained by Raman spectroscopy

The thermodynamic transition temperature is a key parameter to ascertain when assessing the properties of a crystalline hydrate. The transition temperature is sometimes difficult to determine experimentally due to rapid transformation between the two crystal forms in solution. In this study, a new approach for determining the transition temperature is presented, utilizing the temperature dependence of the transformation kinetics in aqueous slurries, as determined using in-line Raman spectroscopy. The transition temperatures of several hydrate forming compounds, namely theophylline, carbamazepine and caffeine, are presented. In general, good correlations with literature values were found. This method was found to be a simple, fast and reliable approach for the determination of crystal hydrate transition temperatures in aqueous environments.