Characterization of acetaminophen: molecular microanalysis with Raman microprobe spectroscopy

The in situ spectroscopic identification of acetaminophen in a fatal overdose case is described. Numerous techniques have been used to analyze acetaminophen in biological fluids, however, the use of nondestructive spectroscopic techniques has not been documented. In this investigation, the demonstration of the drug material was established by using the laser Raman microprobe technique, providing an accurate identification by virtue of the drug's molecular fingerprint characteristics. Material found on the deceased was collected and placed on metal (aluminum-coated) plated slides and excited with the 514.5 nm line of an argon ion laser, which was focused to a 1 micron spot size using a high-resolution optical microscope. Spectra of acetaminophen particles with an average size of 5 to 8 microns were obtained. The Raman spectrum of this drug contains characteristic group frequencies assigned to the C = O at 1649 cm-1, the N-H deformation mode at 1620 to 1612 cm-1, the bendstretch mode of the H-N-C = O at 1562 cm-1, the C-H bending mode at 1325 cm-1, and the phenyl ring stretch at 799 cm-1, respectively. The results reported here demonstrate the capability of laser Raman microprobe as a useful adjunct tool for the identification of foreign materials in forensic pathology.