Chemical threat agents (CTAs) are being investigated for chemical attribution signatures (CAS) that are specific to the CTA’s source. Such CAS can provide vital forensic evidence for criminal investigations and prosecutions. In this study, cyanides including 13 KCN and 14 NaCN stocks, from six reported countries of origin were investigated to obtain CAS for source determination. Analysis was conducted for trace anions by high performance ion chromatography (HPIC), carbon stable isotope ratio (δ13C) by isotope ratio mass spectrometry (IRMS) and trace elements by inductively coupled plasma optical emission spectroscopy (ICP-OES). Hierarchical cluster analysis (HCA) of anion profiles showed clustering, irrespective of KCN or NaCN cyanide type, into three distinct groups that corresponded to countries having known solid cyanide factory. The same groups were verified by HCA of elemental and isotopic profiles independently. Variable selection and classification analysis was conducted on anion profiles which were obtained over five years from three separate batches of HPIC analysis using different instruments and operators. Variable selection was performed using Fisher-ratio, interval-PLS, and genetic algorithm based methods. K-nearest neighbors (KNN), PLS-discriminant analysis, and support vector machines were utilized for classification. Classification errors as low as zero were achieved for two validation studies. For classification methods with errors greater than zero, errors were reduced by variable selection. This demonstrated that selected anion impurities provided robust CAS for matching cyanide sample to its factory for stocks analyzed in this study. Anion profiles were also shown to be useful for classification into specific stock or stock group for a subset of cyanide stocks from the same source with cross-validation errors ranging from zero to 5.3%. This work was supported by the Department of Homeland Security Science and Technology Directorate.

Anionic, isotopic, and elemental signatures for forensic source attribution of cyanides

253rd National Meeting (2017)

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