Determination of α-impurities in the β-polymorph of inosine using infrared spectroscopy and X-ray powder diffraction

Abstract

An X-ray powder diffraction method for the quantitative determination of the α-inosine content of mixtures of the crystalline polymorphic forms of α- and β-inosine is described. Oriented sample discs are prepared by pressing with a cellulose binder and the α-inosine content is calculated from measurements of the 8.25 Å and 7.25 Å X-ray diffraction intensities of α- and β-inosine, respectively. The method has a relative deviation of 7% and a detection limit of 0.4%α-inosine. This represents a 35-fold improvement in sensitivity over conventional infrared spectroscopy and a 14-fold improvement over Fourier transform infrared spectroscopy.