Thermal studies on mixtures of benzoic and salicylic acids with cyclodextrins

Rotich, M.K.;Brown, M.E.;Glass, B.D.

Abstract

The thermal behaviour of benzoic and salicylic acids is compared with the behaviour of 1:1 molar ratio physical and kneaded mixtures of these acids with each of three different cyclodextrins (b-, hydroxypropyl-b-, and g-cyclodextrin). Differential scanning calorimetry and thermogravimetry coupled with evolved gas analysis by Fourier transform infrared spectroscopy were used for the thermal studies and X-ray powder diffraction and infrared spectroscopy provided complementary information. Thermal studies of benzoic acid with the cyclodextrins showed significant interactions in both physical and kneaded mixtures of benzoic acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Interactions in the kneaded benzoic acid/g-cyclodextrin mixtures were the most extensive as might be expected for the cyclodextrin with the largest molecular cavity. The results for the salicylic acid/b-cyclodextrin and salicylic acid/hydroxypropyl-b-cyclodextrin mixtures were similar to those for benzoic acid/b-cyclodextrin and benzoic acid/hydroxypropyl-b-cyclodextrin. Again, the kneaded salicylic acid/g-cyclodextrin mixture showed the most interaction.

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1572-8943

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Kluwer Academic Publishers

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Dordrecht, Netherlands

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DOI

10.1023/A:1025402802100