Applications of proton transfer reaction time-of-flight mass spectrometry for the sensitive and rapid real-time detection of solid high explosives

Using recent developments in proton transfer reaction mass spectrometry, proof-of-principle investigations are reported here to illustrate the capabilities of detecting solid explosives in real-time. Two proton transfer reaction time-of-flight mass spectrometers (Ionicon Analytik) have been used in this study. One has an enhanced mass resolution (m/Δm up to 8000) and high sensitivity (～50 cps/ppbv). The second has enhanced sensitivity (～250 cps/ppbv) whilst still retaining high resolution capabilities (m/Δm up to 2000). Both of these instruments have been successfully used to identify solid explosives (RDX, TNT, HMX, PETN and Semtex A) by analyzing the headspace above small quantities of samples at room temperature and from trace quantities not visible to the naked eye placed on surfaces. For the trace measurements a simple pre-concentration and thermal desorption technique was devised and used. Importantly, we demonstrate the unambiguous identification of threat agents in complex chemical environments, where multiple threat agents and interferents may be present, thereby eliminating false positives. This is of considerable benefit to security and for the fight against terrorism.