Forensic analysis of explosive residues from hand swabs

In the forensic examination of physical evidence for organic explosives, cotton swabs are often used to collect residue from surfaces, such as skin and post-blast debris. A preliminary study has been conducted to develop extraction method of a common energetic compound, pentaerythritol tetranitrate (PETN) from hand swabs followed by direct analysis of the resulting extract solution using high-performance liquid chromatography (HPLC) with ultraviolet (UV) detector. Analysis was performed on an octadecylsilane-based (C18) column using acetonitrile-water mixture (55:45) as mobile phase. The mobile phase was pumped at 1.0 mL/min and separation affected using an isocratic mode with the detection wavelength of 230 nm. The explosive residue was extracted from cotton swabs using acetone in an ultrasonic cold bath. The developed method was later applied to the real hand swabs samples, which were taken from three army personnel who handled PETN during a munition disposal operation at Asahan Camp Military Firing range. The acetone extract obtained using sonication method was found to be effective in recovering PETN from cotton swabs with relatively high recovery (89.5%) and good sensitivity with detection limit as low as 2 ng. The content of PETN in the real hand swab samples were found to be in the range of 4.7-130 mg