Explosives residues

Searching a crime scene is a complex process (25), involving poHce, crime scene technicians, and forensic scientists. The procedure requires careful documentation, collection, and preservation of the evidence. Trace evidence (26) in criminal investigations typically consists of hairs (27,28) both natural and synthetic fibers (qv) (29,30), fabrics glass (qv) (31,32) plastics (33) sod plant material budding material such as cement (qv), paint (qv), stucco, wood (qv), etc (34), flammable fluid residues (35,36), eg, in arson investigations explosive residues, eg, from bombings (37,38) (see Explosives and propellents), and so on. 

When impure, the material is unstable towards heat or light and decomposes to give an explosive residue. The pine material is more stable to light, but detonates on heating or in contact with solid alkalies [1], Preparation by action of oxygen on diallylzinc gives improved yields, but there is a risk of explosion. The peroxide is also impact-sensitive if sand is admixed [2],... 

Evaporation of a solution of hexachloroplatinic acid with a deficiency of potassium azide, or with an equivalence of ammonium azide gives explosive residues. Evaporation of a solution of the acid with an equivalence (8 mol) of potassium azide leads to explosion of the cone, solution of the title compound. 

Dissolution of a zinc-ruthenium alloy in hydrochloric acid leaves an explosive residue of finely divided ruthenium [1], More probably this is the hydride, which may decompose on slight stimulus, the evolved hydrogen probably igniting because of the catalytic activity of the metal. Ruthenium prepared from its compounds by borohydride reduction is especially dangerous in this respect [2],... 

Evaporation of an ethereal extract of sulfur caused an explosion of great violence. Experiment showed that evaporation of wet, peroxidised ether gave a mildly explosive residue, which became violently explosive on addition of sulfur. 

TLC is also one of the analytical techniques that is commonly used to support evidence in courts of law. The chemistry concept for visualization is not unique since this reaction scheme, converting explosive to pink dyes, is decades old. TLC provide rapid screening capability for the presence of a broad range of explosive residues. TLC also provides a means for obtaining specificity, i.e., identifying numerous types of explosives, their concentrations, and also provides the capability to ratio the amounts of the explosives present. For example, Comp B has a mixture of RDX and TNT in its formulation, and if present in the sample the ratio would be 60 40, respectively. This ratio becomes visually apparent by the density of the spots with TLC technology (See Figure 2). 

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

Grant et al. [30] found that nitramine and nitroaromatic explosive residues in real field soil samples were stable under refrigeration, but nitroaromatics used to fortify samples degraded rapidly, even when samples were refrigerated. Therefore, fortified soils can lead to significant errors. 

The potential of ultrahigh-resolution mass spectrometry for the analysis of complex chemical mixtures is particularly illustrated by FT-ICR-MS which definitely sets a new standard. For example, ultrahigh-resolution was applied to separate several thousand components in crude oil, [85,86] fuels, [87,88] or explosion residues. [89]... 

M.L. Fultz, Detection and Characterization of Explosives and Explosive Residues, A Review 2001—2004, Interpol Triennial Forensic Science Meeting, Lyon, France, 2004. 

The thermal labOity of many explosives, along with the requirements of high sensitivity, especially in the analysis of post-explosion residues, makes LC/MS a method of choice for the analysis of explosives. Both electrospray ionization (ESI)... 

Characterization and origin identification of explosives is important in forensic analysis of post-explosion residues. In addition to the type of explosive used in a... 

S.L. Richards, R. Sleeman I.F.A. Burton, J.G. Luke, G.T. Carter, W.R. Stott and W.R. Davidson, The detection of explosives residues from hoarding passes. In 7th International Symposium on Analysis and Detection of Explosives, Edinburgh, UK, 2001, p. 60. 

An application well-suited for IMS is the decommissioning and cleanup of sites where extensive manufacturing of explosives has taken place in the last century and where widespread contamination of soils and waters has occurred [74]. Decontamination of model metal scrap artificially contaminated with TNT and of decommissioned mortar rounds stiU containing explosives residue was followed by sampling surfaces with analysis by a portable mobility spectrometer. Mixed anaerobic microbial populations of bioslurries were employed in decontamination of scrap and the mortar rounds, and the IMS analyzer was seen as a sensitive field... 

With a focus on trace forensic detection of explosives, especially for use in counterterrorism and to counter narcotics investigations, Fetterolf et al. [75] evaluated the use of ion mobility-mass spectrometry for explosives determinations. In this, explosives residues were collected on a membrane filter by a special attachment on a household vacuum cleaner. Although subsequent thermal desorption and analysis required only 5 s, fimits of detection for most common explosives were as low as 200 pg. The persistence of explosives on hands and transfer to other surfaces were also examined as were post-blast residues of NG on fragments of improvised explosive devices constructed with double-based smokeless powder. Finally, postblast residue from C-4, Semtex, and other explosives was found by IMS analyses on items of forensic and evidentiary value. These few out of many examples demonstrate that mobihty spectrometers are well suited tools for laboratory and on-site investigations, before and after the use of explosives. 

J.S. Morgan, W.A. Bryden, J.A. Miragliotta and L.C. Aamodt, Improved detection of explosive residues by laser thermal desorption, Johns Hopkins APE Technical Digest 20(3) (1999) 382—395. 

Techniques which may be used for coUection of trace explosives residues at a scene include swabbing with either dry or solvent wetted swabs, sweeping up dust and smaU particles into suitable receptacles, vacuum collection, and the use of a contact heater to coUect semi-volatile materials. If a bomb crater can be located, then samples of the soil from the crater should be sealed in nylon bags for later laboratory analysis. 

Apart from the use of practical explosive tests to assess damage patterns at a crime scene, it has been suggested that patterns of deposition of explosives residue could be similarly assessed [27]. Practical experience shows that even in a planned scientific experiment there are huge variations in residue deposition patterns because of the difficulty of controlling aU the relevant parameters. Events at a crime scene are completely uncontrolled and subject to even greater variations, and to make matters worse the design, placement and performance of the explosive device are at best inferred rather than known. The presence of chemical traces of a particular explosive at a bomb scene is a useful indication of the material used the drawing of any conclusions beyond that point should be subject to extremely cautious consideration. 

J.D. KeUeher, Explosives residue origin and distribution . Forensic Sci. Commim., 4 (2002). 

Army. 1985a. Comparison of extraction techniques and solvents for explosive residues in soil. Order no. A1-5-R0001-XX-A1-48. Aberdeen Proving Ground, MD U.S. Army Toxic and Hazardous Materials Agency. Document no. AD A2205888. 

Bauer CF, Koza SM, Jenkins TF, et al. 1990. Liquid chromatographic method for determination of explosives residues in soil Collaborative study. J Assoc Off Anal Chem 73 541-552. 

U.S. Civil War battlefields, though the latter munitions are usually deteriorated beyond holding any dangerous explosive residue. UXO are also found on former military training facilities, such as Ft. Ord, California, or Kahoolawe, Hawaii. Both these sites have undergone restoration in recent years. 

Figure 8.2 Pattern of concentrated explosive residue, Croatia, Area Reduction Test Site, May/September 2002. Shaded areas represent standing and flowing water to 40 cm deep (Courtesy of Mark Fisher, Nomadics, Inc. Used by permission.)...

Because TNT is an explosive, safety considerations may impose constraints on potential treatment options. Photocatalytic oxidation offers several significant advantages in this regard. Oxidative destruction of the contaminants, rather than separation and concentration, helps prevent the buildup of potentially explosive residues. Low (ambient)-temperature operation circumvents potential problems associated with ignition sources located in close proximity to large quantities of explosive mixtures. These advantages have prompted several examinations of photocatalytic oxidation as potential treatment technology for use in association with TNT, as well as other explosive materials [21-28]. 

The applications of CE analysis to inorganic anions are already numerous and are rapidly growing. The application ranges include, e.g. clinical chemistry [53], the pulp and paper industry [55], environmental samples [49], waste waters from processing plants [56], process control, industrial applications [43,57-59], explosive residue analysis [48], biological samples [60], or drugs and intermediates [61,62]. 

Microspectroscopy applies the identification power of infrared spectroscopy to the microscopic realm. Contaminants on printed circuit boards, blemishes in coatings, and other production defects can be isolated in situ and analyzed (see Electronics, coatings). Analysis of flaws that develop during use illuminates the method of failure. Microscopic samples, such as particulates filtered from air, can be analyzed individually. The forensic applications are many paint chips, single fibers, explosive residues, and inks on currency can all be identified nondestmctively (see Forensic chemistry). The structures of layered materials, such as laminated polymer films, are studied via microspectroscopy by cross-sectioning the materials and examining the individual layers edge on (47). 

Hoffman E.B. Byall, Identification of Explosive Residues in Bomb Scene Investigations , JForensicSci 19 (l), 54-63 (1974) 89) F. 

Midkiff W.D. Washington, Systematic Approach to the Detection of Explosive Residues , JAssoc of AnalChem 59 (6), 1357—74 (1976)... 

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