Novel odour analysis of soils associated with decomposed remains

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NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- The odour produced during mammalian decomposition is a complex mixture of volatile organic compounds (VOCs). Chemical profiling of decomposition odour provides essential knowledge for forensic applications such as insect semiochemistry and victim searches using cadaver-detection dogs and/or portable detection devices. Two major gaps in decomposition odour research were identified; 1) decomposition soil has been poorly characterised in relevant literature, and 2) significant variation exists in the decomposition VOC profile across published studies. This thesis provides a comprehensive characterisation of the decomposition VOC profile in soils associated with decomposed remains and addresses sources of variation by investigating novel VOC collection and analysis techniques. Several field trials were performed using surface-deposited, decomposing human analogues. A preliminary field study was conducted using gas chromatography – mass spectrometry (GC-MS) for the analysis of soil samples in order to investigate the nature of partitioning of decomposition VOCs into soil, and to compare different sorbent-based collection techniques for subsequent studies. The collection of VOCs in situ using sorbent tubes allowed a comprehensive characterisation of VOCs in decomposition soil and identified a wide range of decomposition VOCs that have not been previously reported in research investigating decomposition headspace. A second study was performed investigating residual decomposition VOCs in soil when the decomposing remains were removed from surface deposition sites using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS). This involved the development of a GC×GC-TOFMS method for the analysis of trace decomposition VOCs in soil, and demonstrated the declining nature of specific classes of decomposition VOCs following the removal of remains. GC×GC-TOFMS provided many distinct advantages over the traditional GC-MS approach, and was used to profile decomposition VOCs longitudinally over two field trials performed during different seasons. Major differences in the decomposition VOC trends in soil were observed during these studies, prompting the evaluation of extrinsic factors that influenced decomposition VOC detection using correlation analysis. Finally, a proof-of-concept study was demonstrated using GC×GC coupled with high-resolution TOFMS (GC×GC-HRTOFMS) for the characterisation of decomposition VOCs in soil. This thesis will provide new knowledge of the nature of decomposition odour in soil for forensic applications. Specifically, the implications for cadaver-detection dog alerts are discussed throughout, in an attempt to provide improved chemical knowledge behind anecdotal evidence towards the efficacy of cadaver-detection dogs in forensic casework. The investigation of analytical methods performed herein will also aid in understanding the variation present in literature and provide guidance for future research practices.
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