Transformation of Metastable Forms of Acetaminophen Studied by Thermal Fourier Transform Infrared(FT-IR)Microspectroscopy

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A novel Fourier transform infrared(FT-IR)microspectroscopy equipped with a micro hot stage(thermal FT-IR microscopic system)was used to quickly study the phase transformation of acetaminophen polymorphs by a one-step process. Acetaminophen was sealed in KBr disc on the first and second heating processes under this system. The results indicate that the contour IR profile of form I acetaminophen in the first heating process changed dramatically only near 165℃, but in the re-heating process exhibited a considerable alteration in peak intensity, band width and position near the temperatures at 85, 118 and 153℃. A glassy form of acetaminophen was obtained after rapidly cooling the melted acetaminophen from 200 to 25℃. The glassy acetaminophen was recrystallized at 85℃ to tranform to the form III of acetaminophen in the reheating process, and then transformed to its form II near 118℃. The thermal FT-IR microscopic system is a simple, quick and timesaving tool for investigation of the thermo-dependent molecular structure of acetaminophen polymorphs in the processes of recrystallization and polymorphic transition.
公益社団法人日本薬学会の論文
2002-02-01