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Profiling the chemical composition of explosives

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posted on 2023-05-17, 00:53 authored by Johns, CA, Hutchinson, JP, Michael BreadmoreMichael Breadmore, Rosanne Guijt, Emily HilderEmily Hilder, Gregory Dicinoski, Paul HaddadPaul Haddad

The analysis of post-blast explosive residues has become an essential tool in counterterrorism initiatives.

Explosives based on inorganic salts and peroxides can be constructed using readily available, low cost, and legally purchased components. Examples of their recent use in terrorist bombings include: the Unabomber (USA, 1985–1996), the bombing of the World Trade Center (USA, 1993), the Murrah Federal Building (USA, 1995), several terrorist attacks in Indonesia (2002, 2005) and attacks on public transport systems in Madrid (Spain, 2004) and London (UK, 2005).

Identification of explosives is a topic of considerable interest to forensic scientists and counter-terrorism authorities. The broad area of explosives analysis can be divided into two sub-areas: detection and identification of explosives or their major ingredients prior to detonation (pre-blast screening analysis), or identification of explosives by analysis of debris and residues after detonation (post-blast detection analysis). Pre-blast analysis is a challenging problem that requires the ability to rapidly screen for the presence of inorganic and organic starting materials used to make explosive devices. Such screening is currently being used at fixed locations, such as airport terminals, in efforts to apprehend potential terrorists. On the other hand, post-blast analyses are required to determine the type and composition of an explosive after detonation has occurred. Explosive devices have a vast range of chemical compositions, hence a forensic scientist must be equipped with tools that enable the quantitative analysis of the evidence collected in these cases.

In our laboratory, we develop analytical methods which can be used for both pre-blast and post-blast applications. However the main focus of this article will be on the postblast analysis of “home-made” devices (sometimes also referred to as “improvised explosives” or “improvised explosive devices (IEDs)”) constructed from low explosives. Inorganic home-made explosives employ vigorous oxidation/reduction chemical reactions using strong inorganic oxidisers, such as nitrate, perchlorate or chlorate which can be obtained or refined from commercial sources. High explosives, such as nitrated organic compounds (eg.TNT, RDX, PETN), are much more difficult to obtain because their sale, storage and use are highly regulated.

Some of the analytical methods previously used for the analysis of inorganic explosives include ion chromatography (IC), capillary electrophoresis (CE), scanning electron microscopy-energy dispersion X-ray, mass spectrometry, X-ray powder diffraction, infrared, atomic absorption spectroscopy and various spot tests. However, many of these techniques are not sensitive or specific enough for the analysis of inorganic anions or cations in explosive residues. We have found that the analytical techniques of IC and CE offer complementary, sensitive and selective technology for determining a large range of inorganic ions of relevance to the chemical identification of these types of explosives.

Funding

Dept of Prime Minister & Cabinet

Australian Federal Police

History

Publication title

Chemistry in Australia

Volume

76

Issue

11

Pagination

30-35

ISSN

0314-4240

Department/School

School of Natural Sciences

Publisher

Royal Australian Chemical Institute Inc.

Place of publication

Australia

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the chemical sciences

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