A new polymorphic form of metoprolol succinate.

Only one crystal form of metoprolol succinate (Form I) was reported during previous researches and production. In this study, a new polymorph of metoprolol succinate (here named as Form II) was discovered and investigated by X-ray diffraction, thermoanalysis and infrared spectroscopy. The results show its crystal structure and thermal properties are significantly different with Form I. Compared with Form I, Form II exhibits specific diffraction pattern, lower melting temperature and weaker hydrogen bond effect. The thermostability testing suggests Form II is a metastable crystal form and will gradually transform into Form I undergoing treatment of high temperature and humidity. Metastable crystal form generally has better dissolubility than its corresponding stable form. Subsequent measurement also verified that Form II can dissolve in the water more quickly than Form I.

Thermally induced phase transformation of pearl powder.

The polymorphic phase transformation of thermally treated pearl powder was investigated by X-ray diffraction and thermoanalytical techniques. The phase transformation was based on quantification of the calcite content at various temperatures using Rietveld refinement analysis. The results show that the phase transformation of pearl aragonite occurred within a temperature range of 360-410 °C, which is 50-100 °C lower than the range for non-biomineralized aragonite. These thermoanalytical results suggest that the phase transformation of pearl aragonite may occur immediately after the thermal decomposition of the organic matrix in the pearl powder. An important finding is that decomposition of the organic matrix may greatly facilitate such transformation by releasing additional space for an easier structural reconstruction during the phase transformation process.