Effect of atmospheric pressure on the phase transitions of α,α-trehalose dihydrate DTA study of the dehydration behavior in open systems

Abstract

The phase transitions of α,α-trehalose dihydrate (Th) were investigated by either differential thermal analysis (DTA) with an in-house apparatus of variable-pressure type equipped with an open sample holder or commercially available TG (thermal gravimetry)-DTA apparatus for comparison under the same experimental conditions as to the heating rate (2°C min−1), the type of pan (open), and the particle size of Th (63 μm). The former DTA measurements were carried out under five different total pressures, 101, 75, 61, 48 and 35 kPa, which provided quite helpful information necessary for confirmative assignments of the endothermic peaks due to either melting or dehydration of Th. The usage of largely different amount of Th, 126 and 14 mg for the DTA and TG-DTA measurements respectively, led to their different DTA traces, showing that there were largely different extents of the influence by the measured sample surface exposed to the surrounding atmosphere on its dehydration behavior. In addition the high thermal sensitivity achieved with such mass of Th gave rise to an interesting discovery of an unidentified thermal event at 92°C prior to either melting or dehydration of Th.