Analysis of the volatile organic compounds produced by the decomposition of pig carcasses and human remains
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Complex processes of decomposition produce a variety of chemicals as soft tissues and their component parts are degraded. Among others, these decomposition by-products include volatile organic compounds (VOCs) responsible for the odour of decomposition. Human remains detection (HRD) canines utilize this odour signature to locate human remains during police investigations and recovery missions in the event of a mass disaster. Currently, it is unknown which compounds or combinations of compounds are recognized by the HRD canines. In this study decomposition VOCs were collected from the decomposition headspace of pig carcasses and were analyzed using thermal desorption gas chromatography mass spectrometry (TD-GC-MS). The difficulties associated with the non-target analysis of complex samples led to the further analysis of decomposition odour using a novel application of thermal desorption coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (TD-GCxGC-TOFMS). The additional peak capacity and spectral deconvolution of the GCxGC-TOFMS system generated a characteristic profile of decomposition VOCs across the various stages of soft tissue decomposition. The profile was comprised of numerous chemical families, particularly alcohols, carboxylic acids, aromatics and sulfides. Characteristic compounds identified in this study included 1-butanol, 1-octen-3-ol, 2-and 3-methyl butanoic acid, hexanoic acid, octanal, indole, phenol, benzaldehyde, dimethyl disulfide and trisulfide, which represent potential target compounds of decomposition odour. Currently there is a demand for improved canine training aids and pig carcasses have been proposed as an alternative due to their acceptance as human body analogues. This work investigated the similarities in the decomposition odour profile of pig carcasses and human remains through surface decomposition trials and comparisons to the published literature. It was determined that pig carcasses cannot be eliminated as potential human decomposition odour mimics. Additionally, following the examination of commercially available synthetic training aids, pig carcasses demonstrated a more suitable profile for the training of cadaver dogs. Further investigation into the chemical composition of decomposition odour utilizing TD-GCxGC-TOFMS will aid in determining the signature of human decomposition odour and facilitate the comparisons of these profiles between environments, individuals and species.