The influence of tertiary butyl alcohol and volatile salts on the sublimation of ice from frozen sucrose solutions: implications for freeze-drying.

The purpose of this work was to investigate the phase behavior of tertiary butanol (TBA) and volatile ammonium salts in frozen mixtures with some commonly used excipients and the efficacy of such volatile additives in accelerating the sublimation of ice from frozen solutions. Differential scanning calorimetry was employed to determine first-order phase transformations and glass transition temperatures in binary and ternary mixtures. Ice sublimation rates were studied by conventional freeze-drying and mass loss with time. A eutectic temperature (268 K) was identified for the anhydrous TBA-sucrose system. In frozen ternary water-excipient-TBA systems, the relative amplitudes of the glass and phase transitions, as measured during warming scans, were found to depend critically on the previous cooling rates. Glass transitions of all the freeze-concentrated mixtures used were determined. The sublimation studies indicated an ability of all volatile additives to accelerate ice sublimation from amorphous, freeze-concentrated solutions, but no clear ranking order, applicable to all systems studied, could be established.