Determination of Melting Parameters of Cyclodextrins Using Fast Scanning Calorimetry

Area of Science:

• Physical Chemistry
• Materials Science
• Thermal Analysis

Background:

• Cyclodextrins (CDs) are cyclic oligosaccharides with significant applications in drug delivery and food science.
• Understanding the thermal behavior of CDs, including their melting points and decomposition kinetics, is crucial for optimizing their use in various processes.
• Previous studies have faced challenges in accurately determining CD melting points due to concurrent decomposition at conventional heating rates.

Purpose of the Study:

• To determine the native fusion (melting) points of alpha-, beta-, and gamma-cyclodextrins.
• To investigate the thermal decomposition processes and activation energies of cyclodextrins.
• To provide essential thermal parameters for theoretical models and practical applications involving cyclodextrins.

Main Methods:

• Utilized fast scanning calorimetry (FSC) with heating rates up to 40,000 K s^-1.
• Employed conventional differential scanning calorimetry (DSC) with heating rates from 4 K min^-1 for comparison.
• Analyzed endothermal effects to distinguish decomposition from fusion processes.

Main Results:

• Successfully registered the first evidence of native cyclodextrin fusion using FSC.
• Identified limiting temperatures at high heating rates as the true melting points for α-, β-, and γ-cyclodextrins.
• Determined activation energies for thermal decomposition, revealing lower stability for β-cyclodextrin compared to α- and γ-cyclodextrins.

Conclusions:

• High heating rates in FSC effectively suppress decomposition, allowing for accurate determination of cyclodextrin melting points.
• The distinct thermal stability of β-cyclodextrin is attributed to preliminary phase transitions and reactions without mass loss.
• The obtained fusion parameters are vital for predictive models of solubility and dissolution rates, and for the preparation of cyclodextrin inclusion compounds.