1986 Volume 34 Issue 4 Pages 1784-1793
The effect of grinding in an agate centrifugal ball mill at 200 rpm on the physicochemical properties of indomethacin (IMC) polymorphs was studied by means of X-ray diffraction analysis, infrared spectroscopy and differential scanning calorimetry. The α and γ forms (metastable and stable forms) of IMC were ground at 4°C ant at 30±0.5°C, and the degree of crystallinity (Xc) of the ground products was measured by the X-ray diffractional internal standard method.The Xc of the γ form ground at 4°C decreased with increasing grinding time, and was 0% after 4 h, that is, the γ form had been converted to a noncrystalline solid. After grinding for 1 h at 30°C, about 45% of γ form of IMC was converted to noncrystalline solid, while the product ground for 10 h was transformed to the α form.The Xc of the α form ground for 2 h at 4°C was 0%, that is, the αform had been converted to a noncrystalline solid within 2 h at 4°C. The Xc of the α form ground at 30°C decreased with increasing grinding time and the value after 10 h was about 60%.The solubility in distilled water at 35°C of the γ form ground for 10 h at 4°C was about 60% larger than that of the intact γ form. The solubilities of the γ form gournd for 10 h at 30°C, the α form gound for 10 h at 4°C and the α form gound for 10 h at 30°C were all the same, 0.94 mg/100 ml, which is equal to that of the α form at 35°C.