Slurry and Emulsion Explosives: New Tools for Terrorists, New Challenges for Detection and Identification

Abstract

With advantages in cost, safety and ease of use, water gel/slurry and emulsion explosives are rapidly replacing traditional explosives. As a result, cap sensitive versions of each are increasingly encountered in criminal activity and a strategy for their identification and characterization is needed. A water gel/slurry explosive is essentially an aqueous solution of an inorganic oxidizer gelled with a carbonaceous gelling agent. Dispersion of fuel or additional oxidizer in the gel produces a slurry, the "water gel explosive" of co=erce. Added sensitizers enhance intiation to a detonator with particular compounds protected by patent and specific to a producer. When intact material is available for examination, sensitizer and other component identification characterizes the explosive type. Emulsion explosives, more efficient than gels, differ in that, emulsifying agents suspend droplets of aqueous oxidizer solution in an oil phase. Chemical sensitizers may be used in emulsion explosives but are less co=on than in slurry types. Most emulsions are sensitized by microspheres, tiny glass bubbles which both control density and provide "hot spot" initiation. Physical characteristics and composition of typical slurries and emulsions, combined with a systematic analytical approach, are used for the characterization and discrimination of intact gel/slurry and emulsion explosives.

Forensic identification of explosive oxidizers by electrospray ionization mass spectrometry

“…Inorganic oxidizers are widely used as blasting agents in commercial explosives used in mining and construction,1 and also in improvised home‐made explosive devices 2. Black Powder, also known as gunpowder, was the first explosive composition, containing potassium nitrate as oxidizer.…”

Analysis of oxidizer salt mixtures by electrospray ionization mass spectrometry

“…7 Ammonium nitrate is thermally less stable than other common oxidizers, and undergoes decomposition at temperatures above 2108C to produce nitrous oxide and water. 8 At heated capillary temperatures below 1508C in ESI-MS positive ion mode, clusters corresponding to [(NH 4 NO 3 ) i NH 4 ] þ (i ¼ 1-3) were reported. 3 The higher thermal stability of other common oxidizers allowed cluster ions to be observed at capillary temperatures as high as 2508C.…”

“…3,4 However, many commercial blasting agents contain mixtures of oxidizer salts, and therefore it is instructive to examine the ESI-MS response to mixtures of oxidizer salts. 8,11 In addition to commercial blasting agents, improvised or 'homemade' bombs have been reported to contain multiple oxidizer salts, depending on the availability of materials; for example, the bombs used in the 2002 Bali bombing contained chlorates/perchlorates. In this paper we examine the ESI mass spectra of a series of solutions containing two oxidizer salts formed of singly charged cations and anions.…”

The Identification of the Emulsifier Component of Emulsion Explosives by Liquid Chromatography‐Mass Spectrometry

“…Compared with traditional organic explosives, there are relatively few studies on the forensic identification of emulsion explosives and their postblast residues (2)(3)(4)(5)(6)(7)(8). Previous studies rely on the analysis of the oxidizer compounds, hydrocarbons, and other components such as aluminium flakes and glass microballoons.…”