Vapor Pressures of RDX and HMX Explosives Measured at and Near Room Temperature: 1,3,5-Trinitro-1,3,5-triazinane and 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane

Abstract

Knowing accurate saturated vapor pressures of explosives at ambient conditions is imperative to provide realistic boundaries on available vapor for ultra-trace detection. In quantifying vapor content emanating from low-volatility explosives, we observed discrepancies between the quantity of explosive expected based on literature vapor pressure values and the amount detected near ambient temperatures. Most vapor pressure measurements for low-volatility explosives, such as RDX (1,3,5-trinitro-1,3,5-triazinane) and HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), have been made at temperatures far exceeding 25 °C and linear extrapolation of these higher temperature trends appears to underestimate vapor pressures near room temperature. Our goal was to measure vapor pressures as a function of temperature closer to ambient conditions. We used saturated RDX and HMX vapor sources at controlled temperatures to produce vapors that were then collected and analyzed via atmospheric flow tube-mass spectrometry (AFT-MS). The parts-per-quadrillion (ppqv) sensitivity of AFT-MS enabled measurement of RDX vapor pressures at temperatures as low as 7 °C and HMX vapor pressures at temperatures as low as 40 °C for the first time. Furthermore, these vapor pressures were corroborated with analysis of vapor generated by nebulizing low concentration solutions of RDX and HMX. We report updated vapor pressure values for both RDX and HMX. Based on our measurements, the vapor pressure of RDX at 25 °C is 3 ± 1 × 10–11 atm (i.e., 30 parts per trillion by volume, pptv), the vapor pressure of HMX is 1.0 ± 0.6 × 10–14 atm (10 ppqv) at 40 °C and, with extrapolation, HMX has a vapor pressure of 1.0 ± 0.6 × 10–15 atm (1.0 ppqv) at 25 °C.

Vapor Signatures of Double-Base Smokeless Powders and Gunshot Residues for Supporting Canine Odor Imprinting

“…In fact, by optimizing reaction times for chemical ionization, nitrate adducts can even be used for detecting ambient vapor from RDX, 43 which at saturation is still in the low ppt range. 39 Lastly, we note that nitroaromatics like DNT and TNT do not form nitrate adducts as readily, 58 so interferences from those compounds are not expected (i.e., interference from DNT in the powder is not expected). For diphenylamine, the signal was lower.…”

Non-contact real-time detection of trace nitro-explosives by MOF composites visible-light chemiresistor

“…3 e, Supplementary Fig. S7 and Supplementary Table S1) [ 29 , 30 ]. A noticeable response to 0.8 ppq was observed (insets in Fig.…”

Explosive molecule sensing at lattice defect sites in metallic carbon nanotubes

“…Fig. 5 plots the current-voltage characteristics of all five sensors, where the plotted response is the current increment defined by eqn (3). As expected from the zero-bias conductance results, the current changes for oxygen adsorption are relatively high, hence they are presented separately on a sixth plot which includes results for all five sensor types.…”

“…Trace detection of explosive materials 1 presents a wide range of challenges. 2 In the gas phase, high sensitivity is often needed to address low vapor pressures, 3 while good selectivity 4 is required to distinguish target analytes from background gases and other explosive molecules. There is considerable demand for mobile, low power sensing systems to replace mass spectrometers 5 or other traditional explosive detection devices which can be bulky, complex, and expensive.…”