Thermal analysis behavior of β- and γ-cyclodextrin inclusion complexes with capric and caprilic acid

The inclusion complex of capric (C10) and caprilic (C8) acids with β- and γ-cyclodextrins (CDs) was analyzed, in the solid state, by differential scanning calorimetry (DSC), thermogravimetry (TGA), and infrared spectroscopy (FT-IR). Special attention was paid to the acid behavior in terms of the quantity incorporated and the thermal stability. The results showed that the maximum amount of incorporated acid in β-CD occurred at molar ratio (CD:acid) of 1:1 and 1:1.5 for C10 and C8, respectively. For the same acids in γ-CD, the proportions increased to 1:1.5 (C10) and 1:2 (C8). The heat for the water volatilization was higher in γ-CD (ca. 91 cal g−1) than β-CD (ca. 52 cal g−1) systems, for both acids, probably because of the high cavity size of γ-CD. Although, both systems improved additional thermal stability with the complex formation, the acids acquired a higher thermal stability in the β-CD inclusion complex.