title: Whisker growth of l-menthol in coexistence with various excipients.
abstract: The purpose of the present study was to clarify the mechanism for l-menthol whisker growth. l-Menthol was mixed with an excipient, and the interaction was examined by IR measurement, thermal analysis and powder X-ray diffraction. Then we examined the involvement of the capillary condensation using the pore size distribution measurement. By mixing l-menthol with an excipient with whisker growth, the hydroxyl group stretching band of l-menthol was shifted to the higher wavenumber in the IR spectrum, the melting point and heat of fusion of l-menthol became lower in the thermal analysis, and the diffraction intensity of l-menthol became lower in the powder X-ray diffraction. The excipients with whisker growth showed the tendency to have the meso-pore involved in the capillary condensation in the pore size distribution measurement. From the above results, the whisker growth mechanism is considered as follows. When l-menthol was mixed with an excipient with whisker growth, the crystallinity of l-menthol was lowered and the vapor pressure was increased by the interaction mainly consisting of the hydrogen bond. The generated l-menthol vapor entered meso-pore, the saturated vapor pressure was lowered by the capillary condensation, and the nucleation occurred. The vapor was further supplied, generating the growth of whisker.
authors.affiliation: Laboratory of Medical and Pharmaceutical Technology, School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, 192-0392, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yuasa
authors.forename: M
authors.initials: M
authors.lastname: Ooi
authors.forename: Y
authors.initials: Y
authors.lastname: Takashima
authors.forename: Y
authors.initials: Y
authors.lastname: Kanaya
mesh_terms: D003460:Crystallization; D005079:Excipients / Q000008:administration & dosage*; D006358:Hot Temperature; D008610:Menthol / Q000008:administration & dosage* / Q000737:chemistry; D013055:Spectrophotometry, Infrared
chemical_list: D005079:Excipients; D008610:Menthol