Analysis of pre-ignited improvised incendiary devices using portable Raman

Martín-Alberca, Carlos; Lopez‐López, María; García-Ruiz, Carmen

doi:10.1016/j.talanta.2015.06.072

Cited by 8 publications

(2 citation statements)

References 19 publications

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“…[16][17][18] In addition, the non-invasive analysis of pre-ignited IIDs (classic Molotov cocktails and CIMCs) by portable-Raman was recently reported by our research group. 19 In the case of analyzing classic Molotov cocktails, the complete identification of several neat ILs in glass bottles of different characteristics was achieved, and it was also possible to identify gasoline and sulfuric acid in CIMCs. However, in the CIMC case the derived compounds of the reactions between gasoline compounds and sulfuric acid showed intense fluorescence impeding their identification at certain times by Raman.…”

Section: Introductionmentioning

confidence: 99%

Study of Spectral Modifications in Acidified Ignitable Liquids by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy

2016

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In this work, the spectral characteristics of two types of acidified gasoline and acidified diesel fuel are discussed. Neat and acidified ignitable liquids (ILs) infrared absorption spectra obtained by attenuated total reflection Fourier transform infrared spectroscopy were compared in order to identify the modifications produced by the reaction of the ILs with sulfuric acid. Several bands crucial for gasoline identification were modified, and new bands appeared over the reaction time. In the case of acidified diesel fuel, no significant modifications were observed. Additionally, the neat and acidified ILs spectra were used to perform a principal components analysis in order to confirm objectively the results. The complete discrimination among samples was successfully achieved, including the complete differentiation among gasoline types. Taking into account the results obtained in this work, it is possible to propose spectral fingerprints for the identification of non-burned acidified ILs in forensic investigations related with arson or the use of improvised incendiary devices (IIDs).

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Section: Introductionmentioning

confidence: 99%

Study of Spectral Modifications in Acidified Ignitable Liquids by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy

2016

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“…Based on the chemical composition of petroleum fuels, one would expect reaction with sulfuric acid to cause a variety of chemical changes in fuel due to reactions between the sulfuric acid and native compounds in the fuel [2][3][4]. Gasoline fuel exhibits substantial chemical changes due to the presence of tert-butylating compounds, such as methyl tert-butyl ether (MTBE), while the changes to diesel fuel are more subtle, limited to the aromatic moiety of the fuel [2,4]. For the purposes of forensic classification of acid altered diesel fuel, it is necessary to better understand the chemical compositional changes that occur and which may differentiate unaltered from altered fuels.…”

Section: Introductionmentioning

confidence: 99%

Chemical characterization of the acid alteration of diesel fuel: Non-targeted analysis by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry with tile-based Fisher ratio and combinatorial threshold determination

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Pinkerton

Wright

et al. 2016

Journal of Chromatography A

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The illicit chemical alteration of petroleum fuels is of keen interest, particularly to regulatory agencies that set fuel specifications, or taxes/credits based on those specifications. One type of alteration is the reaction of diesel fuel with concentrated sulfuric acid. Such reactions are known to subtly alter the chemical composition of the fuel, particularly the aromatic species native to the fuel. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) is well suited for the analysis of diesel fuel, but may provide the analyst with an overwhelming amount of data, particularly in sample-class comparison experiments comprised of many samples. Tile-based Fisher-ratio (F-ratio) analysis reduces the abundance of data in a GC×GC-TOFMS experiment to only the peaks which significantly distinguish the unaltered and acid altered sample classes. Three samples of diesel fuel from differently branded filling stations were each altered to discover chemical features, i.e., analyte peaks, which were consistently changed by the acid reaction. Using different fuels prioritizes the discovery of features likely to be robust to the variation present between fuel samples and may consequently be useful in determining whether an unknown sample has been acid altered. The subsequent analysis confirmed that aromatic species are removed by the acid alteration, with the degree of removal consistent with predicted reactivity toward electrophilic aromatic sulfonation. Additionally, we observed that alkenes and alkynes were also removed from the fuel, and that sulfur dioxide or compounds that degrade to sulfur dioxide are generated by the acid alteration. In addition to applying the previously reported tile-based F-ratio method, this report also expands null distribution analysis to algorithmically determine an F-ratio threshold to confidently select only the features which are sufficiently class-distinguishing. When applied to the acid alteration of diesel fuel, the suggested per-hit F-ratio threshold was 12.4, which is predicted to maintain the false discovery rate (FDR) below 0.1%. Using this F-ratio threshold, 107 of the 3362 preliminary hits were deemed significantly changing due to the acid alteration, with the number of false positives estimated to be about 3. Validation of the F-ratio analysis was performed using an additional three fuels.

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