A Novel Standard Sample Powder Preparation Method for Quantitative Analysis of Polymorphs

Abstract

The purpose of this study was to improve the sensitivity and accuracy of the quantitative analysis of polymorphic mixtures. Calibration curve reliability has been improved through the advancement of standard mixture preparation techniques whereby samples at scales of several grams are homogeneously and accurately prepared without decrease in crystallinity. Crystalline powders are first micronized to anisotropic, nearly equal-sized (<10 μm) particles of almost random orientation in an air jet mill. These powders are then mixed in a vibration mill that includes rubber balls as mixing media. Using this technique, α and γ forms of indomethacin (IMC) were prepared in various proportions from 0.5% to 50% α content and subjected to X-ray powder diffraction analysis. The validation data showed that these precisely prepared standard mixtures resulted in superior analytical sensitivity and accuracy compared to those prepared by agate mortar. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association