Browsing by Subject "explosives"
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(2022)Chemical attribution encompasses the detection and characterization of compounds of interest to find signature impurity, isotopic, and elemental profiles, which can be used to link illegal material to specific manufacturers, stocks, precursors, synthetic routes, or geographical locations. Explosives have been increasingly used for criminal purposes world-wide due to the availability of explosive material, precursors, and synthesis instructions. Nitrate ester, nitramine, and nitroaromatic military explosives as well as homemade organic peroxides are examples from over 250 explosive materials listed in the 2020 Federal Register of the US Bureau of Alcohol, Tobacco, Firearms, and Explosives. The first part of the thesis is a literature review, which aims to 1) present published mass spectrometric (MS) and liquid chromatographic (LC) detection methods for explosives and 2) explore chemical attribution studies of explosives and related compounds, such as illicit drugs and chemical warfare agents. The second part presents the experimental research carried out at the Finnish Institute for Verification of the Chemical Weapons Convention (VERIFIN), which aims to 3) develop an analysis method for multiclass explosives using liquid chromatography-high resolution mass spectrometry (LC-HRMS) and 4) perform chemical attribution of the nitrate ester explosive pentaerythritol tetranitrate (PETN) from different sources by isotopic and impurity profiling. Multiclass explosives detection required optimization of MS parameters, such as lower ion transfer tube and vaporizer temperatures and negative ion detection mode, as well as introduction of additives into LC eluents to promote adduct formation. PETN, 1,3,5-trinitro-1,3,5-triazinane (RDX), 1,3,5,7-tetranitro- 1,3,5,7-tetrazocane (HMX), 2,4,6-trinitrophenyl-methylnitramine (tetryl), 2-amino-4,6-dinitrotoluene (2- ADNT), and 4-amino-2,6-dinitrotoluene (4-ADNT) were detected from a mixture as nitrate adducts. Optimal parameters for the isotopic profiling of PETN were found to be 500 000 resolution, 2E4 (5 %) automatic gain control (AGC) target, and 50 ms injection time. Student’s t-tests revealed statistically significant differences between oxygen isotope ratio (18O/16O) values of PETN from two different sources. However, lack of repeatability of the isotope ratio results was an issue. 7 different methods were tested for the impurity profiling of PETN. Samples were rather pure but clear differences in the high mass range (m/z 600–900) impurity profiles of the two types of PETN were discovered, leading to the conclusion that they are indeed from different sources. Tentative structures of PETN homologue derivatives were assigned to the impurities using MS2 fragmentation and literature. Based on the results of this work, LC-HRMS is suitable for impurity analysis even for pure samples, but not very efficient or practical for analyzing isotope ratios.
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(2011)Here, we demonstrate the application of desorption atmospheric pressure photoionization (DAPPI) as a screening method at the Criminal Laboratory of the Finnish National Bureau of Investigation for samples confiscated by the Finnish criminal police. DAPPI is a fast mass spectrometric technique to analysis compounds directly from the sample surface in ambient atmosphere. In DAPPI, the sample is thermally desorbed from the sample surface using hot solvent vapor, after which the analytes are ionised in the gas-phase by photon-initiated gas-phase reactions. DAPPI was applied to the direct analysis of confiscated drugs, anabolic steroids and explosives of various matrices without any sample preparation. Confiscated drug samples included e.g. tablets, powders, herbal mixtures, herbal products [Catha edulis (khat) leaves, opium, Cannabis sativa, Psilocybe mushrooms] and ampules and tablets containing anabolic steroids. Powders were sprinkled on a 2-sided tape on a microscope slide, after which the excess powder was shaken away from the tape surface. Liquid samples were analysed from a kitchen paper, after application of 1 Äl of oil from ampules. Other samples were analysed by simply placing them on the DAPPI sampling stage and by directing the solvent plume on the sample surface. DAPPI proved to be a fast and specific analysis technique to this type of forensic analysis. DAPPI does not require any sample preparation, which therefore is well suited for fast forensic analysis, especially for plant samples and oily anabolic steroids, which are considered very challenging with conventional methods. Contamination of the mass spectrometer could be avoided by adjustment of the distance of the sample from the mass spectrometer inlet. Memory effects or contamination of the MS instrument were not observed even after several weeks of DAPPI measurements. DAPPI was also used for trace detection of the explosives trinitrotoluene (TNT), nitroglycol (NK), nitroglycerine (NG), penitrit (PETN), cyclonite (RDX), octogen (HMX) and picric acid. These organic explosives are nitrated compounds, which are divided based on their chemical structure into nitroaromatics (TNT and picric acid), nitroamines (RDX and HMX) and nitrate esters (PETN, NG and NK). Explosive dilutions were analysed with DAPPI from a polymer surface [poly(methyl methacrylate), PMMA] after application and drying of 1 Äl of sample. Also forensic analysis of post-blast residues from different matrices were done. DAPPI was effective in the ionisation of nitroamines and nitrate esters as their adducts with anions such as nitrate, acetate, formate and acetate. TNT used to form negative molecular ions through electron capture and picric acid formed deprotonated molecules through proton transfer. A DAPPI-MS method was developed for all explosives but the identification of the very low concentration explosive traces from wild variety of matrices proved to be difficult.
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