Identification of Improvised Inorganic Explosive Devices by Analysis of Postblast Residues Using Ion Chromatography and Capillary Electrophoresis

Abstract

Chemical analysis of the residues from improvised explosive devices (IEDs) has become a topical subject as a result of increased frequency of terrorist bomb attacks. There is a need to identify the type of explosive device and its composition, which in turn can assist in the identification of the perpetrators. IEDs can either be organic based (high explosives) or the more easily produced inorganic‐based low explosives. Analysis of residues remaining after the deflagration of an inorganic IEDs presents several problems. A wide variety of ionic species may be present (such as unconsumed starting products, ionic species formed as part of the reaction) along with environmental or background species. Therefore, it is important that the target ions used to identify the device can be separated from other background ions present in the sample. The instrumental techniques of capillary electrophoresis (CE) and ion chromatography (IC) are proving to be ideally suited to this task. Both techniques have fundamental advantages, with CE offering highly efficient separations within a short run time, and IC offering high selectivity, sensitivity, and reproducibility. In this article, an outline of the analytical methods used in this area is presented, with particular focus on the application of CE and IC. A brief literature review of published methods is provided, along with background information on inorganic explosives, sampling techniques, portable instrumentation, and recent developments.

Identification of Inorganic Improvised Explosive Devices Using Sequential Injection Capillary Electrophoresis and Contactless Conductivity Detection

“…The accurate identification of explosive residues requires the discrimination between explosive tracer ions and background ions in order to avoid false positive or false negative identifications. On the basis of our previous work in this area ,,, chloride, sulfate, phosphate, and to a lesser extent fluoride and thiocyanate are the most probable background ions likely to be present in preblast or postblast samples. The presence of background levels (low milligram per liter) chloride, sulfate, nitrate, and fluoride in samples taken from a variety of surfaces has recently been confirmed, while thiocyanate is likely to be present as a residue of cigarette smoke.…”