从火灾残骸中提取具有代表性的石油基可燃液体,用于犬类展品的验证性分析

R. J. Abel, J. Harynuk
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摘要

火灾碎片分析的重点是可燃液体的回收和识别,为火灾调查提供背景。调查人员使用多种方法选择可疑碎片进行分析,可燃液体探测犬是最受欢迎的方法之一。经过适当培训和认证后,可燃液体检测犬可以提供高灵敏度的连续采样,并能够区分无关气味和可疑气味,以快速定位可能含有可燃液体残留物的碎片。然而,犬科动物的适应症是推定的,因为如果没有确证的实验室分析,法律程序就无法对其进行充分的审查。标准碎片分析方法检测极少量的可燃液体残留物(~1-0.1μL),而没有最大限度地提高灵敏度,从而将误报和检测环境中普遍存在的背景石油的风险降至最低。对于犬类选择的碎片,实验室分析的目标应该是提供数据来确认或反驳犬类适应症的有效性。为了使这种验证性分析有用,分析灵敏度应接近犬的灵敏度。提取装置的选择和提取条件的调整对火灾碎片分析的灵敏度影响最大。无损提取是法医分析的首选,固相微萃取(SPME)是一个很好的选择。然而,原始SPME纤维是脆弱的,并且倾向于扭曲色谱图谱,这可能导致高成本和可燃液体错误分类的风险。在此,我们提出了一种优化的SPME提取方法,适用于犬类选定展品的验证性分析。该方法具有无损性和非详尽性,易于应用于碎片罐,产生的色谱图谱与基于活性炭的金标准被动顶空进样(PHS)方法获得的色谱图谱相当。对纤维选择、碎片温度、纤维温度和提取时间进行了优化,以产生与作为纯液体或标准PHS提取物收集的参考样品具有最大可比性的色谱图谱。优化的方法适用于从另一项研究中回收的样本,该研究估计了犬类的敏感性阈值,并将实验室结果与每个样本的犬类结果进行了比较。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Sensitive and Representative Extraction of Petroleum-Based Ignitable Liquids From Fire Debris For Confirmatory Analysis of Canine-Selected Exhibits
Fire debris analysis is focused on the recovery and identification of ignitable liquids to provide context for fire investigation. Investigators use a variety of methods to select suspicious debris for analysis, with ignitable liquid detection canines being one of the most popular. When properly trained and certified, ignitable liquid detection canines offer continuous sampling with high sensitivity and the ability to discriminate between irrelevant and suspicious odours to rapidly locate debris which may contain ignitable liquid residues. However, canine indications are presumptive as they cannot be sufficiently scrutinised by the legal process without confirmatory laboratory analysis. Standard debris analysis methods detect very small amounts of ignitable liquid residue (∼1-0.1 μL) without maximising sensitivity which minimises the risk from false positives and from detection of background petroleum which is ubiquitous in our environment. For canine-selected debris, the goal of the laboratory analysis should be to provide data to confirm or refute the validity of the canine indication. For such confirmatory analysis to be useful, analytical sensitivity should approximate the sensitivity of the canine. The sensitivity of fire debris analysis is most influenced by the selection of the extraction device and tuning of extraction conditions. Non-destructive extractions are preferred for forensic analyses, and solid phase microextraction (SPME) offers an excellent option. However, the original SPME fibres are fragile and tend to skew the chromatographic profile which can lead to high costs and a risk of ignitable liquid misclassification. Herein, we present an optimised SPME extraction method suited to confirmatory analysis of canine-selected exhibits. The method is non-destructive and non-exhaustive, is easily applied to cans of debris, and yields chromatographic profiles equivalent to those obtained by the gold-standard passive headspace sampling (PHS) methods based on activated carbon. Fibre selection, debris temperature, fibre temperature, and extraction time were optimised to yield chromatographic profiles with maximum comparability to reference samples collected as neat liquids or standard PHS extracts. The optimised method is applied to samples recovered from another study which estimated the threshold of the canine’s sensitivity, with the laboratory result compared to the canine result for each sample.
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