Investigation Into the Detection of Nitrated Organic Compounds and Explosives by Direct Chemiluminescent Emission During Thermally Induced Gas Phase Decomposition Reactions

Abstract

The selective detection of explosive compounds by gas phase chemiluminesence is investigated. When the vapour from a range of explosive compounds was heated, including nitrate esters and nitramines, a blue–green chemiluminescent emission was observed during the decomposition process. This phenomenon occurred at sub atmospheric pressures, after pure vapour was admitted into a heated and evacuated reaction vessel. However, the emission intensity was increased when helium or nitrogen gas was used to assist the transport of the vapour into the reaction vessel. Limits of detection under static reaction conditions were obtained for a number of compounds, for example, 0.013 Pa isopropyl nitrate in 1.3 × 10 ⁴ Pa helium. The chemiluminescent reaction of a number of explosive compounds was examined in a flow reactor. Samples could be directly injected, or admitted after gas chromatographic separation. It was observed that the simple alkyl nitrates (e.g., ethyl nitrate and propyl nitrate) were more stable than cyclotrimethylene trinitramine (RDX) and pentaerythritol tetranitrate (PETN), and thus gave a lower limit of detection. This method offers the potential for enhanced selectivity over current detection methods for explosive compounds of forensic interest.