Non-isothermal dehydration kinetic study of aspartame hemihydrate using DSC, TGA and DSC-FTIR microspectroscopy

作者：Hsieh Wei hsien^*; Cheng Wen ting; Chen Ling chun; Lin Shan yang^*

来源：Asian Journal of Pharmaceutical Sciences, 2018, 13(3): 212-219.

DOI：10.1016/j.ajps.2017.12.001

• Aspartame (APM) hemihydrate
• DSC/TGA
• DSC-FTIR
• Dehydration
• Activation energy
• DKP formation

Three thermal analytical techniques such as differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) using five heating rates, and DSC-Fourier Transform Infrared (DSC-FTIR) microspectroscopy using one heating rate, were used to determine the thermal characteristics and the dehydration process of aspartame (APM) hemihydrate in the solid state. The intramolecular cyclization process of APM anhydrate was also examined. One exothermic and four endothermic peaks were observed in the DSC thermogram of APM hemihydrate, in which the exothermic peak was due to the crystallization of some amorphous APM caused by dehydration process from hemihydrate to anhydride. While four endothermic peaks were corresponded to the evaporation of absorbed water, the dehydration of hemihydrate, the diketopiperazines (DKP) formation via intramolecular cyclization, and the melting of DKP, respectively. The weight loss measured in TGA curve of APM hemihydrate was associated with these endothermic peaks in the DSC thermogram. According to the Flynn-Wall-Ozawa (FWO) model, the activation energy of dehydration process within 100-150 degrees C was about 218 +/- 11 kJ/mol determined by TGA technique. Both the dehydration and DKP formation processes for solid-state APM hemihydrate were markedly evidenced from the thermal-responsive changes in several specific FTIR bands by a single-step DSC-FTIR microspectroscopy.

• 出版日期2018-5