Thermal characterization of natural and modified cyclodextrins using TG-MS combined technique

Thermoanalytical techniques (TG, DSC) are frequently used in the investigation of the thermal properties of cyclodextrins and their inclusion complexes. However, the above techniques do not provide information on the chemical composition of the evolved fragments upon the thermal decomposition. In this study alpha-, beta- and gamma-cyclodextrins and 4 methylated and 3 ethylated beta- CD derivatives were investigated with a TG-MS combined thermoanalytical technique in order to get information about their fragmentation behaviour. By comparison of the TG/DTA curves, a different thermal behaviour was found for each of the native and the chemically modified cyclodextrins. Except for the water loss profiles and the solid-solid phase transformations, the thermal behaviour of the ( investigated) native CDs do not show remarkable differences. However, the chemical modification of the native beta-CD resulting in a new compound may change the strength of interactions between host and guest causing differences in the thermal stabilities of the derivatives. The mass spectrometry results supported the observed thermal differences and showed significant alterations in the fragmentation of ethylated and methylated compounds. The investigated natural CDs possess a very similar fragmentation profile, due to the common alpha-D-glucopyranose building units. In the case of modified CDs characteristic signals of the substituents are present.