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There is a need to develop a wider empirical research base to expand the scope for utilising the organic fraction of soil in forensic geoscience, and to demonstrate the capability of the analytical techniques used in forensic geoscience to discriminate samples at close proximity locations. The determination of wax markers from soil samples by GC analysis has been used extensively in court and is known to be effective in discriminating samples from different land use types. A new HPLC method for the analysis of the organic fraction of forensic sediment samples has also been shown recently to add value in conjunction with existing inorganic techniques for the discrimination of samples derived from close proximity locations. This study compares the ability of these two organic techniques to discriminate samples derived from close proximity locations and finds the GC technique to provide good discrimination at this scale, providing quantification of known compounds, whilst the HPLC technique offered a shorter and simpler sample preparation method and provided very good discrimination between groups of samples of different provenance in most cases. The use of both data sets together gave further improved accuracy rates in some cases, suggesting that a combined organic approach can provide added benefits in certain case scenarios and crime reconstruction contexts. [ABSTRACT FROM AUTHOR]

A key issue for geoforensic analysis is the ability to discriminate between geographical locations of close proximity, often with similar underlying geology. This paper addresses the lack of empirical research into the non-mineral components of sediment samples and presents the development of a method of sediment sample characterisation by High Performance Liquid Chromatography (HPLC) utilising the organic components of the sample. A sample preparation method and set of instrument parameters were developed such that the cost of the analysis could be reduced, efficiency increased and the sample amount required for analysis reduced fourfold. The re-developed method allows samples collected from different locations within the same forensically relevant site to be accurately discriminated in this study by both visual examination of the chromatography and the use of multivariate statistics. The results of the HPLC analysis were compared with those obtained by quartz grain surface texture analysis, and HPLC was found to offer better discrimination between the samples in this instance. The results of this study suggest that HPLC has the potential to offer an accurate and practical method of comparing soil samples based on characteristics that are independent of, and therefore complementary to, traditional mineralogical-based geoforensic analyses. [ABSTRACT FROM PUBLISHER]

Soil is a highly transferable source of trace physical material that is both persistent in the environment and varied in composition. This inherent variability can provide useful information to determine the geographical origin of a questioned sample or when comparing and excluding samples, since the composition of soil is dependent on geographical factors such as climate, bedrock geology and land use. Previous studies have limited forensic relevance due to the requirement for large sample amounts and unrealistic differences between the land use and geographical location of the sample sites. In addition the philosophical differences between the disciplines of earth sciences, for which most analytical techniques have been designed, and forensic sciences, particularly with regard to sample preparation and data interpretation have not been fully considered. This study presents an enhanced technique for the analysis of organic components of geoforensic samples by improving the sample preparation and data analysis strategies used in previous research into the analysis of soil samples by high performance liquid chromatography (HPLC). This study provides two alternative sets of marker peaks to generate HPLC profiles which allow both easy visual comparison of samples and the correct assignment of 100% of the samples to their location of origin when discriminating between locations of interest in multivariate statistical analyses. This technique thereby offers an independent form of analysis that is complementary to inorganic geoforensic techniques and offers an easily accessible method for discriminating between close proximity forensically relevant locations. [ABSTRACT FROM AUTHOR]