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Download fileSolution-Mediated Polymorphic Transformation of FV Sulphathiazole
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posted on 02.07.2014, 00:00 authored by Áine Munroe, Denise M. Croker, Åke C. Rasmuson, Benjamin
K. HodnettThe
solution-mediated polymorphic transformation of FV sulphathiazole
was investigated in ethanol at 10 °C. Powder X-ray diffraction
(PXRD) identified the transformation product as a mixture of FII and
FIV sulphathiazole. This mixture remained stable in solution at 10
°C with agitation for 24 h. In situ temperature controlled optical
microscopy enabled visualization of the transformation in real time,
allowing elucidation of the transformation mechanism. A modest amount
of dissolution of FV sulphathiazole preceded the nucleation of FII
and FIV crystals, which were detected simultaneously. Thereafter,
these polymorphs grew rapidly. Experimental evidence is presented
for a mechanism, whereby nucleation of FII and FIV was initiated on
the roughened surface of the dissolving FV crystals, without any indication
for a spatially extended structural relationship between the host
form V and the nucleating phases. Subsequent growth of FII and FIV
crystals consumed the remaining FV crystals completing the dissolution-recrystallization
mechanism.