Bulk and trace detection of ammonia and hydrogen peroxide using quantum cascade laser technology - a tool for identifying improvised explosive devices

Abstract

The type of explosive materials used in terrorist activities has seen a gradual shift from those that are commonly manufactured but difficult to obtain, such as trinitrotoluene (TNT) and nitroglycerine (NG), to improvised explosive devices (IEDs) made from substances that are more readily available. This shift has placed an emphasis on development of instruments capable of detecting IEDs and their precursors, which are often small, volatile molecules well suited to detection through mid-infrared absorption spectroscopy. Two such examples are ammonia, a breakdown product of ammonium nitrate and urea nitrate, and hydrogen peroxide, an efficient oxidiser used in the production of triacetone triperoxide (TATP) and hexamethyl triperoxide diamine (HMTD). At this meeting in 2007 we presented results of a hydrogen peroxide detection portal utilising quantum cascade laser (QCL) technology. This trace detection system has since undergone significant development to improve sensitivity and selectivity, and the results of this will be presented alongside those of a similar system configured for bulk detection of ammonia. Detection of ammonia produced from the breakdown of ammonium nitrate has been demonstrated, both on the optical bench and in a walkthrough portal. This research has been supported by the UK government.