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Analytical Methods Used for the Discrimination of Substances Suspected to be Bar Soap: A Preliminary Study

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The submission to forensic laboratories of unknown specimens suspected of being biological or chemical warfare agents has increased tremendously with the threat of terrorism. Oftentimes, a threatening correspondence that contains hoax materials is intended to make the recipient(s) believe they have been exposed to a toxin. In some cases, the perpetrator can use standard household products, such as detergents and soaps. Once these materials are received, they become forensic evidence and may be analyzed for identification and/or comparison with known seized material from a suspect(s). Two separate studies were conducted using different analytical protocols for bar soaps. In the first set, the forensic laboratory at the United States Secret Service conducted tests on 68 bars of soap using solid-phase microextraction and gas chromatography coupled with mass spectrometry. The 68 different soaps displayed unique total ion chromatogram profiles. Energy-dispersive X-ray analysis in conjunction with scanning electron microscopy was also used to characterize 46 of the 68 soaps as a preliminary study. In a second set of studies, as part of a homicide investigation, the laboratory at the California Department of Justice, Riverside, conducted examinations on 13 bars of soap by utilizing Fourier transform-infrared spectroscopy. The case study demonstrated that it is possible to distinguish some bar soaps using infrared analysis. Furthermore, the bar soaps could be distinguished from typical laundry detergents using this technique.
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Keywords: FT-IR; GC/MS; SEM; SPME; bar soap; forensic science; soap; surfactants; trace evidence; unknown substances

Document Type: Research Article

Affiliations: 1: United States Secret Service, Forensic Services Division, Questioned Document Branch, Washington, DC 20223. 2: United States Secret Service, Forensic Services Division, Washington, DC 20223. 3: California Department of Justice, Riverside Criminalistics Laboratory, 7425 Mission Blvd., Riverside, CA 92509.

Publication date: 2006-11-01

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