Analysis of Explosives

An explosion occurs when energy that was previously confined is suddenly released to affect the surroundings. Small-scale explosions, such as a shaken can of fizzy juice exploding, are harmless however, explosions such as those produced to demolish a building are an example of the opposite extreme of a scale. Explosives are chemical compounds or mixtures of chemical compounds in which much energy is stored this energy should be able to be released quickly in order to provide the energy to be classed as an explosive. 

An explosive can be defined as a sudden or violent release of physical or chemical energy, often accompanied by the emission of heat, light, and sound (White 2004). Explosions can be characterised by their source of energy (i.e., whether that source is physical or chemical) and also by whether the explosion is in the dispersed or condensed phase. The following are examples of the different types of classes of explosion  

Explosives can also be classified by the detonation velocity at which they release the confined energy. This classification differentiates explosives as 

---

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

Giesbrecht, H., K. Hess, W. Leuckel, and B. Maurer, 1981. Analysis of explosion hazards on spontaneous release of inflammable gases into the atmosphere. Part 1 Propagation and deflagration of vapor clouds on the basis of bursting tests on model vessels. Ger. Chem. Eng. 4 305-314. 

Giesbrecht, H., K. Hess, W. Leuckel, and B. Maurer. 1981. Analysis of explosion hazards... 

E. S. Erancis, M. Wu, R B. Eamswoith and M. L. Lee, Supercritical fluid extraaion/gas cliromatography with thermal desorption modulator interface and niti O-specific detection for the analysis of explosives , 7. Microcolumn Sep. 7 23-28 (1995). 

Oleum. Fuming sulfuric acid a soln of sulfur trioxide in sulfuric acid used as a sulfating and sulfonating agent. See under Acidity in Acids in Vol 1, A88-R to A90-R Acids Used in Manufacture and Analysis of Explosives in Vol 1, A93-L to A93-R and under Nitration in this Vol For analytical procedures, see under Glass Bulbs for Weighing Acids in Vol 6, G78-R to G79-R... 

Yinon, J. und Zitrin, S. The Analysis of Explosives, Pergamon Press, Oxford, New York 1981... 

A. Hilmi and J.H.T. Luong, Micromachined electrophoresis chip with electrochemical detectors for analysis of explosive compounds in soil and groundwater, Environ. Sci. Technol., 34 (2000) 3046-3050. 

I. A. Buryakov, Express analysis of explosives, chemical warfare agents and drugs with multicapillary column gas chromatography and ion mobility increment spectrometry, J. Chromatogr. B, 800 (2004) 75-82. 

Yinon, J. and Zitrin, S., Modern Methods and Applications in Analysis of Explosives, John Wiley Sons, New York, 1996. 

Grace, T. M., and Taylor, M. L. (1979). Analysis of Explosion Data. Inst. Pap. Chem., Appleton, Wisconsin. 

The main drawback of the use of color reactions for the analysis of explosives lies in their often low specificity. Although their specificity varies according to the type of reactions - and some reactions are quite specific - it is generally not safe enough to establish an identification of an explosive in a forensic laboratory on color reactions alone. When the color is obtained, the key question is whether other compounds, which are not explosives, can produce the same color under identical experimental conditions. Unfortunately, the answer is usually, yes. Thus, in forensic analysis, where an erroneous identification may lead to a gross injustice, it is generally accepted that the identification of an explosive should not depend on color reactions alone. 

Reliable identification of explosives in a modem forensic laboratory is based on instmmental techniques, mainly spectrometric, often in conjunction with chromatographic methods. Gas chromatography—mass spectrometry (GC/MS) is considered to be an excellent and reliable method in forensic analysis, including the analysis of explosives. 

Color reactions are used in the laboratory in conjunction with thin-layer chromatography (TLC) — a routine and highly popular method for the analysis of explosives (for a full review, see Ref. [1, chapter 5, pp. 59—85] and Ref [2, chapter 2, pp. 33—41]). Spots on the TLC plates are visuaHzed by spraying the plates with appropriate color reagents. 

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. 

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]. 

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 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)... 

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. 

Mass spectrometry, and especially LC/MS, is a major technique in the analysis of explosives. It combines good sensitivity and selectivity, and in addition to MS/ MS, provides an excellent identification tool for the forensic analyst. 

J. Yinon Analysis of explosives hy LC/MS. In J. Yinon, (ed.). Advances in Forensic Apphcations of Mass Spectrometry, CRC Press, Boca Raton, 2003. 

Calculations can also be helpful. The defence departments of various countries have developed sophisticated computer codes for the prediction and analysis of explosive effects. However not only are these not generally published which makes forensic review and scrutiny difficult, but they are also designed for use with mifitary materials and may be less applicable to home-made explosives. 

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. 

McLuckey SA, Glish GL, Carter JA. 1985. The analysis of explosives by tandem mass spectrometry. J Forensic Sci 30 773-788. 

J. Pennington, and T. Berry. Analysis of Explosive-Related Chemical Signatures in Soil Samples Collected Near Buried Landmines. U.S. Army Engineer Research and Development Center—Cold Regions Research and Engineering Laboratory, ERDC-CRREL, Report ERDC TR-00-5, Hanover, NM, March 2000. 

---