Probing the thermal transitions of lactobionic acid and effects of sample history by DSC analysis

© 2019 American Pharmacists Association® We report the results of an ad hoc evaluation of the thermal transition and physical state of lactobionic acid, carried out by differential scanning calorimetry, which was motivated by the confusion about its physical state in relation to the “melting point.” This work establishes that lactobionic acid is a molecular glass characterized by a glass-liquid transition at around 125°C and 2 minor transitions, respectively, at around 70°C and 40°C. The temperature at which these latter transitions appear and the intensity of the enthalpic peaks, associated with physical aging, are sensitive to the thermal history of the sample and to the presence of small quantities of absorbed water.