Trace Analysis of Explosives

Trace analysis of explosives is of major importance in forensic and environmental applications [6]. In forensics, the applications include analysis of postexplosion residues and identification of traces of explosives on suspects hands, clothing and other related items. The results of these analyses are not only necessary for the investigation of a bombing but can also serve as evidence in court. 

In the environmental field, the applications include analysis of explosives and their degradation products in soil and water. These analyses are important because of the toxicity of most explosives and the fact that many areas in the vicinity of explosives and munitions manufacturing plants are contaminated. 

The methodologies for the analysis of explosives for both forensic and environmental applications are very similar, using mainly GC/MS and LC/MS. As explosives are thermally labile compounds, LC/MS has an obvious advantage over GC/MS, as the chromatography is carried out at room temperature. 

Several examples illustrate the use of GC/MS for analysis of explosives Trace analysis of explosives in water by GC/MS was carried out using a cooled temperature-programmable injector and a 15 mx 0.255 (Xm ID, 0.25 (Xm film thickness, DB-1 column [7]. 

A study comparing detection limits for GC/MS analysis of 2,4-DNT, TNT, RDX and PETN, using El, Cl and NICI, showed that NICI gave the lowest detection fimits, which were between 0.18 and 1.11 ng [8]. 

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FAST TRACE ANALYSIS OF EXPLOSIVE VAPORS. STATUS AND PROSPECTS... 

Solid-phase microextraction (SPME) for preconcentration, followed by GC/ Ion Trap MS, was used for trace analysis of explosives and their metabolites in seawater [9]. NICI was used with methane as reagent gas. Compounds of interest included RDX, TNT and two of its metabofrtes 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT). Although the instrument sensitivity was in low-ppb range, the detection limits for SPME with GC/ITMS... 

The following examples illustrate the range of apphcations of LC/MS for trace analysis of explosives ESI-LC/MS/MS-CID fragmentation processes of a series of nitroaromatic, nitramine and nitrate ester explosives were studied in the negative-ion mode using daughter-ion, parent-ion and neutral loss scans [14]. Table 1 shows the CID daughter ions in ESI-MS/MS of TNT. 

J.M.P. Douse, Trace analysis of explosives at the low nanogram level in handswab extracts using columns of Amberlite XAD-7 porous polymer beads and sdica capillary column gas chromatography with thermal energy analysis and electron capture detection , J. Chromatogr., 328 (1985) 155-165. 

Although the reported sensitivity of TEA when it is used in combination with HPLC or packed column GC to analyse explosives is only in the low nanogram range, Douse [21] described a method that uses fused silica capillary column GC in conjunction with TEA detection for trace analysis of explosives in the low picogram range. He reported that silica capillary column GC can be used to overcome the problems of very polar explosives adsorbing on the packed columns used for GC analysis and in the transfer lines of the TEA. In this way, the detection limits were lowered. He also concluded that the minimum detectable levels (15,10 and <200pg for NG, TNT and RDX, respectively) of the compounds studied were similar to those obtained when ECD was used. 

J. M. F. Douse, 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, Journal of Chromatography 234 (1982) 415. 

Douse JMF. 1982. Trace analysis of explosives in hand-swab extracts using Amberlite XAD-7, porous beads, silica capillary-column gas chromatography with electron-capture detection and thin-layer chromatography. J Chromatogr 234 415-425. 

Barshick, S.-A. and W.H. Griest. 1998. Trace analysis of explosives in seawater using solid-phase microextraction and gas chromatography / ion trap mass spectrometry. Anal. Chem. 70 3015-3020. 

Kolia R, Gas chromatography, liquid chromatography and ion chromatography adapted to the trace analysis of explosives, J. Chromatogr, 674, 309-318, 1994. 

Kolia, P. Trace analysis of explosives from complex mixtures with a sample preparation and selective detection. J. Forensic Sci. 1991, 36, 1342-1359. 

Trace analysis of explosives in postblast debris samples requires a detector considerably more sensitive than an FID. ECD, nitric oxide detection (TEA), and GCMS have all been nsed for the chromatographic detection of explosives (209). Gas chromatographic analysis with specific detection is normally used for screening purposes. Other methods, such as TLC, microscopy, X-ray diffraction (XRD), and SEM, are often used to confirm the presence of trace... 

Mass spectrometry has become a routine technique for forensic analysis of explosives and one of the technologies used for vapor and trace detection of hidden explosives. 

Reception arrangements need to provide for checking the safety of items being submitted, separation of items to prevent cross-contamination, initial identification of submitted material, and the preparation of aU the requisite documentation. After items have been received and documented they wiU need to be transferred to an appropriate storage area, whether this be for trace analysis, biohazard, explosive, flammable, toxic, or bulk debris. It is advisable to have pre-planned quarantine storage for anything whose characteristics or provenance cannot be guaranteed. 

X. Xu, A.M. van der Craats, E.M. Kok and P.C.A.M. de Bruyn, Trace analysis of peroxide explosives by high performance liquid chromatography — atmospheric pressure chemical ionization — tandem mass spectrometry (HPLC-APCl-MS/MS) for forensic applications ,... 

The analysis of explosives has rather obvious forensic implications. HPLC applications have been published concerning both the analysis of postblast residues in the attempt to identify the explosive used, and the detection of explosive traces on the hands and clothing of a suspect in order to provide... 

Inspired by the effective post-column photochemical conversion of hydroperoxides and peroxides to H2O2 just described, a method was developed for trace analysis of peroxide explosives, such as triacetone triperoxide (251) and hexamethylene triperoxide diamine (252). These are powerful explosives with no commercial or military applications because... 

Blosser, Research in Trace Analysis of Ultrapure Explosives. Part II. Spark Source Mass Spectro-graphic Analysis of Azides , PATR 4014 (1970), (AD 707 934) 37) R.T.M. Fraser, Analysis... 

The results of an analysis for explosives are used as evidence to show that an individual has been handling explosives. A whole batch of evidence had to be rejected because it was found that the inside of a centrifuge used in the analysis had become contaminated with trace amounts of explosive from a broken centrifuge tube. It was not possible for the laboratory to prove beyond reasonable doubt that no cross contamination had occurred. 

GC coupled with IMS has many advantages and is applied for quality control in the pharmaceutical industry [131, 132] and for detection of trace amount of explosives, warfare agents, and drugs [133-135]. This system is used to monitor ambient air [136] and for direct analysis of exhaled air [137]. 

Hobbs J. R. and Conde E. P, A simple inexpensive thermal desorption method for the trace analysis of headspace vapors from explosives and organic nitro-Compounds, Proceedings of Interernational Symposium on Forensic Aspects Trace Evidence, FBI Quantico, VA, June 24-28, 1991, 269. Avail. NTIS PB94-145877. 

Wakelin, D. (2000) Isotopic ratio analysis of explosives traces—a new type of evidence. United Kingdom Defence... 

While IMS and MS are both widely used for explosives analysis, hybrid IM-MS instruments have recently been applied to detect explosives [186]. The lack of HLS-related research with IM-MS systems may be in part due to the availability of commercial IM-MS systems [183,187]. However, this hybrid technique offers a distinct advantage over both IMS and MS alone the ability to simultaneously separate samples by both mobility and mass. This twofold separation mechanism greatly decreases the likelihood of a mass or mobility interfer-ent masking the signal of the analyte of interest. In complex, real-world samples where matrix effects may significantly inhibit the detection of trace amounts of explosive material, the ability to separate in two dimensions (2D) is extremely powerful [188]. Figure 20.16 shows a typical 2D IM-MS plot of black powder with... 

In trace detection, on the other hand, chemical analysis methods are applied to check for the existence of trace contamination of explosives on a passenger s body, clothes, and luggage [1]. Trace detection methods have higher selectivity capabilities than bulk detection methods, and the false-positive rate is typically below 1%. However, even if an explosive contamination is confirmed or detected on a bag or passenger, the bag or passenger may not actually be carrying the explosive device at that time. 

Schulte-Ladbeck, R., Kolia, P., Karst, U. Trace analysis of peroxide-based explosives. Anal. Chem. 75, 731-735 (2003)... 

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