X-Ray powder diffraction determination of the relative amount of crystalline acetaminophen in solid dispersions with polyvinylpyrrolidone

A powder X-ray diffraction technique has been developed to quantify the relative amounts of crystalline acetaminophen in powder mixtures with polyvinylpyrrolidone prepared by blending and recrystallisation. Four methods were used to prepare solid dispersions of acetaminophen and PVP: (a) mechanical mixing in a tumbling mixer or planetary ball mill, (b) co-precipitation, (c) freeze-drying and (d) recrystallisation. Changes in X-ray powder diffraction properties and the differences in solubilities showed that the amount of crystalline acetaminophen only decreased in mixtures where both acetaminophen and polyvinylpyrrolidone were soluble (ethanol) or partially soluble (water). The decrease in the amount of crystalline material was the result of the formation of a glass-like, amorphous solid solution, The formation of this amorphous material could be followed by X-ray diffraction analysis of powdered samples. (C) 1998 Elsevier Science B.V. All rights reserved.