Trace Analysis Of Explosives Research Articles

Evaluation of selected SERS substrates for trace detection of explosive materials using portable Raman systems

Raman spectroscopy has become an essential analytical technique for field detection and identification of illicit or dangerous materials such as explosives, but its main drawback is low signal intensity. This problem can be circumvented by using surface enhanced Raman spectroscopy (SERS), in which scattering signals increase significantly for analytes adsorbed onto or near nanostructured surfaces of the plasmonic materials. However, despite numerous studies, SERS has still not been widely used in real-world applications. The main goal of the studies describe herein was to investigate the possibility of detection of trace amounts of selected explosive materials on various commercial and non-commercial SERS substrates using portable Raman instruments. Our studies have shown that while portable systems suitable for SERS measurement of trace amounts of explosives are readily available, the problem remains in the selection of reliable and reproducible SERS substrates. Among five investigated SERS substrates only two, Klarite 312 and GaN-pillars allowed for trace analysis of all studied explosive materials. In both cases, detected concentrations of explosives ranged from single to hundreds of μg/cm2 depending on the explosive material and the Raman spectrometer used. Based on our findings, it could be concluded that the best SERS substrates for trace analysis of explosives are substrates with hot spots densely and evenly distributed over a whole active area of SERS substrate.

Quality assurance testing of an explosives trace analysis laboratory — Further improvements to include peroxide explosives

The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol:water mixture, in equal amounts. The swabs are then extracted, cleaned up and analysed using Gas Chromatography with Thermal Energy Analyser detectors or Liquid Chromatography with triple quadrupole Mass Spectrometry. This paper follows on from two previous published papers which described the regime and summarised results from approximately 14years of tests. This paper presents results from the subsequent 7years setting them within the context of previous results. It also discusses further improvements made to the systems and procedures and the inclusion of quality assurance sampling for the peroxide explosives TATP and HMTD. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti-contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated.

Mass Spectrometry for Trace Analysis of Explosives in Water

Harmful explosives can accumulate in natural waters over the long term during their testing, usage, storage, and dumping and can pose a health risk to humans and the environment. Mass spectrometry (MS) has become the most successful technology for the analysis of such compounds in water throughout the North America and Europe. During the past decade, improvements have occurred for MS analysis in understanding explosives ion behavior and the influence of additives and reagent gases on the formation of ions. Novel approaches also have been developed for fast MS analysis of explosives. These advances motivated an update from previous discussions of MS response to explosives. Recent findings collected from the past ten years have been assessed to provide a comprehensive view of the detection of explosives by MS. This review focuses on the most commonly used MS-based methods and newer developments for the MS analysis of explosives in water, with particular attention to mass identified ions and the performance of the methods. We also include results from comparative studies of explosives detection involving MS-methods that use various ionization techniques.

Ordered gold nanoparticle arrays as surface-enhanced Raman spectroscopy substrates for label-free detection of nitroexplosives

Nitroexplosives, such as 2,4,6-trinitrotoluene (TNT) which is a leading example of nitroaromatic explosives, are causing wide concern. Motivated by the urgent demand for trace analysis of explosives, novel surface-enhanced Raman spectroscopy substrates based upon highly ordered Au nanoparticles have been fabricated by a simple droplet evaporation method. It is noteworthy that an ethylhexadecyldimethyl ammonium bromide bilayer surrounding each individual nanoparticle not only is responsible for these periodic gap structures, but also tends to promote the adsorption of TNT on the composite NPs, thus resulting in a considerable increase of Raman signal. These desirable features endow the resulting SERS substrates with excellent enhancement ability and allow for a label-free detection of common plastic explosive materials even with a concentration as low as 10 −9 M.

Quality Assurance Testing of an Explosives Trace Analysis Laboratory––Further Improvements

The Forensic Explosives Laboratory (FEL) operates within the Defence Science and Technology Laboratory (DSTL) which is part of the UK Government Ministry of Defence (MOD). The FEL provides support and advice to the Home Office and UK police forces on matters relating to the criminal misuse of explosives. During 1989 the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could, if other precautions failed, result in the contamination of samples and controls. Designated areas within the laboratory are swabbed using cotton wool swabs moistened with ethanol water mixture, in equal amounts. The swabs are then extracted, cleaned up and analyzed using Gas Chromatographs with Thermal Energy Analyzer detectors. This paper follows on from a previous published paper describing the regime and summarizing subsequent results from approximately 6 years of tests. Lessons learned and improvements made over the period are also discussed. Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has demonstrated that in this environment the risk of forensic sample contamination, assuming all the relevant anti-contamination procedures have been followed, is so small that it is considered to be negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated.

Trace Analysis of Explosives in Soil: Pressurized Fluid Extraction and Gas and Liquid Chromatography-Mass Spectrometry

Soil samples are collected from the former Open Burn/Open Detonation Unit, Makua Military Reservation, on the island of Oahu, Hawaii. The soil is the Helemano series. The soil samples are fortified with eight explosives for development of the analytical method. These analytes are 2-amino-4,6-dinitrotoluene; 1,3-dinitrobenzene; 2,4-dinitrotoluene (DNT); hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX); nitrobenzene (NB); octogen; 1,3,5-trinitrobenzene; and 2,4,6-trinitrotoluene. The analytes are recovered with pressurized fluid extraction and measured with liquid chromatography (LC), LC-mass spectrometry (MS), and gas chromatography-MS. Average recoveries of the seven analytes, except for NB, range from 67% to 110% from freshly fortified samples. The procedure fails to extract NB in soil. The average recoveries decrease from 67-110% to 41-81% as the soil is aged for 1 day to 6 months after fortification of the soil with the seven explosives. The field samples are analyzed for the presence of explosives, of which DNT and RDX are indeed detected. The results obtained with this procedure agree well with those obtained by an independent laboratory following the standard U.S. Environmental Protection Agency (EPA) method SW-846 8330. Compared with the EPA method, this new method provides MS confirmation of the analytes, and the extraction requires approximately 15 min, rather than 18 h by the EPA method.

Quality Assurance Testing of an Explosive Trace Analysis Laboratory

During 1989, the Forensic Explosives Laboratory (FEL) established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels which could, if other precautions failed, result in the contamination of samples and controls. This paper describes the regime and summarizes the results from approximately eight years of tests. Lessons learned and improvements made over the period are also discussed.

Trace Analysis of Explosives in Seawater Using Solid-Phase Microextraction and Gas Chromatography/Ion Trap Mass Spectrometry

Complex matrixes typically cannot be analyzed directly to obtain the selectivity and sensitivity required for most trace analysis applications. To circumvent this problem, solid-phase microextraction (SPME) techniques were used to preconcentrate analytes selectively prior to gas chromatographic/ion trap mass spectrometric analysis. This approach was applied to the trace analysis of explosives and their metabolites in seawater. The choice of SPME sorbent phase was shown to be important especially for the amino metabolites of trinitrotoluene (TNT) and RDX, which were extracted better on polar phases. Although equilibration times were quite lengthy, on the order of 30 min or greater, a sampling time of only 10 min was shown to be sufficient for achieving low part-per-billion (ppb) to part-per-trillion (ppt) detection limits for TNT and the amino metabolites in real seawater samples. While SPME was ideal for rapid screening of explosives in seawater samples, methods for improving the reproducibility and accur...

Trace analysis of explosives in water by gas chromatography—mass spectrometry with a temperature-programmed injector

Gas chromatography—mass spectrometry with a cooled temperature-programmable injector was used to analyze picogram amounts of explosives in water. The analyzed explosives included 2,4,6-trinitrotoluene (TNT), 2,4,6-N-tetranitro-N-methylaniline (Tetryl), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX), pentaerythritol tetranitrate (PETN) and a series of dinitrotoluene (DNT) isomers (which are ingredients of explosives). Thermal decomposition, even in the thermolabile explosives, was minimal. Traces of explosives in water in the range of 5–100 ppb could be detected and identified.

Gas chromatography, liquid chromatography and ion chromatography adapted to the trace analysis of explosives

The potential of gas chromatography, high-performance liquid chromatography and ion chromatography for application to the determination of traces of explosives was investigated. The most important aspect is the combination of the chromatographic technique with selective detection methods. In gas chromatography a chemiluminescence detector is preferred and for high-performance liquid chromatography the advantages of postcolumn derivatization are described. Problems and possible solutions in the trace analysis of explosives which depend on matrix effects and chemical properties are discussed.

Trace Analysis of Explosives from Complex Mixtures with Sample Pretreatment and Selective Detection

Abstract The analysis of explosive traces in different samples from criminal investigations is described. An important step for the analysis is sample preparation with solid-phase extraction. The analytical procedure is preferably performed with gas chromatography and nitro/nitroso-specific detection. The commercially available detection unit was modified. Possible solutions for the confirmation of the identity of an explosive trace are outlined.

Trace analysis of explosives by capillary supercritical fluid chromatography with thermal energy analysis detection

Trace analysis of explosives by capillary supercritical fluid chromatography with thermal energy analysis detection

Improved method for the trace analysis of explosives by silica capillary column gas chromatography with thermal energy analysis detection

Improved method for the trace analysis of explosives by silica capillary column gas chromatography with thermal energy analysis detection

Trace analysis of explosives by thermospray high-performance liquid chromatography—mass spectrometry

A series of explosives were analyzed by thermospray high-performance liquid chromatography—mass spectrometry (TSP-HPLC—MS). Both positive and negative ion spectra were acquired in thermospray and chemical ionization (filament-on) modes. The explosives proves most sensitive in the negative ion mode under chemical ionization conditions. The spectra for the explosives analyzed provided molecular weight information with few fragment ions. Detection limits from 200 pg for trinitrotoluene to 5 ng for ammonium picrate were obtained under full scan mass spectrometer conditions. TSP-HPLC—MS proved useful in separating and identifying components in commercial explosive mixtures without interferences from plasticizers as well as in detecting explosives from hand swabs with excellent sensitivity and specificity. The plasticizers primarily were detected in the positive ion mode while the explosives were most sensitive with negative ion detection.

Trace analysis of explosives and firearm discharge residues in the metropolitan police forensic science laboratory

Abstract Improved methods were developed for the isolation and purification of explosives traces on handswabs. Silica capillary column gas chromatography with electron capture detection was used to analyse the cleaned-up extracts. The methods were applied to the analysis of nitroglycerine in firearm discharge residues deposited on hands and clothing by various weapons and different types of ammunition. We also describe improvements in the thin layer chromatography of nitroaromatic explosives on handswabs using an iminobispropylamine spray to form charge transfer complexes.

Trace analysis of explosives at the low nanogram level in handswab extracts using columns of amberlite xad-7 porous polymmer beads and silica capillary column gas chromatography with thermal energy analysis and electron-capture detection

Thermal energy analysis (TEA) was compared with electron-capture detection (ECD) for the analysis of explosives both as pure compounds and in spiked handswabs by silica capillary column gas chromatography. TEA was shown to approach the sensitivity of ECD but was more selective, enabling low nanogram levels of explosives in handswabs to be detected. Use of TEA in the nitrogen mode for drug analysis was also briefly studied.

Trace analysis of explosives at the low picogram level using silica capillary column gas chromatography with thermal energy analyser detection

Trace analysis of explosives at the low picogram level using silica capillary column gas chromatography with thermal energy analyser detection

Trace analysis of explosives in handswab extracts using Amberlite XAD-7 porous polymer beads, silica capillary column gas chromatography with electron-capture detection and thin-layer chromatography

A general method for detecting traces of explosives at the low nanogram level in hardswab extracts is described. The method involves a preliminary clean-up using Amberlite XAD-7 porous polymer beads to remove interfering lipid material, followed by detection of explosives in the concentrated extracts by capillary column gas chromatography with electron-capture detection. A method for confirming the presence of explosives in the extracts using thin-layer chromatography is also described.

Trace analysis of explosives at the low picogram level by silica capillary column gas—liquid chromatography with electron-capture detection

Trace analysis of explosives at the low picogram level by silica capillary column gas—liquid chromatography with electron-capture detection