Analysis of N-(4-hydroxyphenyl)retinamide polymorphic forms by X-ray powder diffraction

A quantitative X-ray diffraction method, with zinc oxide used as the internal standard, was developed for the analysis of polymorphic forms I and II of N-(4-hydroxyphenyl)retinamide. The standard curve relating peak height ratio to the percentage of form I was linear. The method was precise and accurate to within +/- 6%.