Detection of amorphous-amorphous phase separation in small molecular co-amorphous mixtures with SEM-EDS

European Journal of Pharmaceutics and Biopharmaceutics : Official Journal of Arbeitsgemeinschaft Für Pharmazeutische Verfahrenstechnik E.V
Katja PajulaOssi Korhonen

Abstract

Amorphicity is one possible way to increase the solubility of poorly water soluble drugs. However, amorphous solids are thermodynamically unstable and tend to recrystallize with material-specific kinetics. Crystallization is not the prime phenomenon in the whole process, although it is the easiest to measure. The primary phenomenon prior to the crystallization of glass is phase separation, the detection of which is very rarely reported among small molecular compounds. In the present study, a scanning electron microscope with energy dispersive X-ray spectrometer (SEM-EDS) was used to detect very early stage amorphous-amorphous phase separation in co-amorphous drug mixtures. Miscibility was calculated for five studied mixtures based on the Flory-Huggins method and four immiscible pairs and one partial miscible pair were selected for the laboratory experiments. Co-amorphous samples (n=3) were prepared by melt-quench method and stored at the elevated temperature to induce the separation of amorphous phases. Each sample was stored at the same relative percentage temperature between glass transition temperature Tg and melting temperature Tm. Immediately after the sample preparation, the full amorphousness was verified with polarizing...Continue Reading

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