New methods for preparing cyclodextrin inclusion compounds. I. Heating in a sealed container.

A new method for preparing a solid inclusion compound was developed. A physical mixture of benzoic acid and α-or β-cyclodextrin (CD) or the ground mixture was sealed in a container after adsorbing a definite amount of water vapor, then heated to a temperature ranging from 43 to 142 °C. The results of powder X-ray diffraction and infrared spectroscopy showed that the crystalline inclusion compound was produced when the container was heated at over 70°C. The combining molar ratio of benzoic acid to α-CD in the inclusion compound prepared by this method was higher than that obtained by the coprecipitation method. Physical mixtures of benzoic acid and α-or β-CD were also sealed in a stainless steel vessel under nitrogen gas pressure, then heated to 127 °C. The pressurized samples had a higher combination ratio than the non-pressurized samples.