Affiliations: Department of Pharmaceutical Technology, Kobe Pharmaceutical University, Higashi-Nada, Kobe 658, Japan | Department of Pharmaceutics, University of Utah, Salt Lake City, UT 84112, USA
Note: [] Requests for reprints should be addressed to Makoto Otsuka, Ph. D., Department of Pharmaceutical Technology, Kobe Phamraceutical University, Motoyama-Kitamachi 4-19-1. Higashi-Nada, Kobe 658, Japan.
Abstract: The effect of environmental conditions on the crystalline transformation of metastable calcium phosphates during grinding was investigated using X-ray diffractometry and fourier transformed infrared spectroscopy. A mixture of CaO and dicalcium phosphate anhydrate (DCPA, CaHPO4) did not transform after grinding in air. On the other hand, CaO and dicalcium phosphate dihydrate (DCPD, CaHPO4 2H2O) were converted into a noncrystalline solid. Mixtures of DCPD and Ca(OH), transformed into low-crystallinity hydroxyapatite after grinding in air. When ground under N2, a mixture of Ca(OH)2 and DCPD did not transform into hydroxyapatite, whereas that of DCPD: Ca(OH)2:CaCO3 = 1:0.8:0.2 did. The results of X-ray diffraction of FT-IR spectra suggested that the presence of carbon dioxide in the grinding system was necessary for transformation from metastable calcium phosphates to hydroxyapatite.
