title: Transformation of metastable forms of acetaminophen studied by thermal Fourier transform infrared (FT-IR) microspectroscopy.
abstract: 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 degrees C, 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 degrees C. A glassy form of acetaminophen was obtained after rapidly cooling the melted acetaminophen from 200 to 25 degrees C. The glassy acetaminophen was recrystallized at 85 degrees C to transform to the form III of acetaminophen in the reheating process, and then transformed to its form II near 118 degrees C. 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.
authors.affiliation: Biopharmaceutics Laboratory, Department of Medical Research & Education, Veterans General Hospital-Taipei, Shih-Pai, Taiwan, Republic of China.
authors.forename: Shun-Li
authors.initials: SL
authors.lastname: Wang
authors.forename: Shan-Yang
authors.initials: SY
authors.lastname: Lin
authors.forename: Yen-Shan
authors.initials: YS
authors.lastname: Wei
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D018712:Analgesics, Non-Narcotic / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D018712:Analgesics, Non-Narcotic; D000082:Acetaminophen