We measured 4 carbonate minerals with different crystalline forms (aragonite, low-Mg calcite, high-Mg calcite, dolomite) using terahertz waves. We found that the crystalline forms or shapes stand out making them clearly distinguishable from the absorption spectrum of the terahertz waves because the terahertz band is extremely sensitive to crystallinity. This now makes it possible to identify carbonate minerals that play an important role in assessing our global environment. Other potential applications of crystal polymorph evaluation include pharmaceutical development and quality control.
Data courtesy of Dr. S. Sakai, JAMSTEC (Japan Agency for Marine-Earth Science and Technology)
ACS Omega 4, 2702-2707 (2019).
While changing the ratio of crystalline nifedipine to amorphous nifedipine we measured the suspension in water. Since the terahertz wave frequency band is very sensitive to crystallinity, we were able to confirm that the absorption peak increases according to the amount of crystal content. Low soluble chemicals such as nifedipine are not absorbed into water while in a crystalline state. This made it essential to find a way to evaluate their crystalline state in water. Making a quantitative evaluation and determining the crystalline and amorphous states are important since these serve as indicators of the stability and solubility of pharmaceutical products and will prove essential for development and quality control of pharmaceuticals.
Takebe et al., J.Pharm.Sci. 102, 4065 (2013).
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