Low- versus Mid-frequency Raman Spectroscopy for <i>in Situ</i> Analysis of Crystallization in Slurries
Jaana Koskela, Joshua J. Sutton, Tiina Lipiäinen, Keith C. Gordon, Clare J. Strachan, Sara J. Fraser‐Miller
Abstract
at 5 and 25 °C with both low- and mid-frequency Raman spectroscopy. At 25 °C, both spectral regions profiled amorphous IND in slurries as converting directly from the amorphous form toward the α crystalline form. In contrast, at 5 °C, principal component analysis revealed a divergence in the detected conversion profiles: the mid-frequency Raman suggested a direct conversion to the α crystalline form, but the low-frequency region showed additional transition points. These were attributed to the appearance of minor amounts of the ε-form. The additional solid-state sensitivity of the low-frequency region was attributed to the better signal-to-noise ratio and more consistent spectra in this region. Finally, the low-frequency Raman spectrum of the ε-form of IND is reported for the first time.