Vapor Pressure of Hexamethylene Triperoxide Diamine (HMTD) Estimated Using Secondary Electrospray Ionization Mass Spectrometry

Abstract

A rapid method for vapor pressure measurement was developed and used to derive the vapor pressure curve of the thermally labile peroxide-based explosive hexamethylene triperoxide diamine (HMTD) over the temperature range from 28 to 80 °C. This method uses a controlled flow of vapor from a solid-phase HMTD source that is presented to an ambient-pressure-ionization mass spectrometer equipped with a secondary-electrospray-ionization (SESI) source. The subpart-per-trillion sensitivity of this system enables direct detection of HMTD vapor through an intact [M + H](+) ion in real time at temperatures near 20 °C. By calibrating this method using vapor sources of cocaine and heroin, which have known pressure-temperature (P-T) curves, the temperature dependence of HMTD vapor was determined, and a Clausius-Clapeyron plot of ln[P (Pa)] vs 1/[T (K)] yielded a straight line with the expression ln[P (Pa)] = {(-11091 ± 356) × 1/[T (K)]} + 25 ± 1 (error limits are the standard error of the regression analysis). From this equation, the sublimation enthalpy of HMTD was estimated to be 92 ± 3 kJ/mol, which compares well with the theoretical estimate of 95 kJ/mol, and the vapor pressure at 20 °C was estimated to be ∼60 parts per trillion by volume, which is within a factor of 2 of previous theoretical estimates. Thus, this method provides not only the first direct experimental determination of HMTD vapor pressure but also a rapid, near-real-time capability to quantitatively measure low-vapor-pressure compounds, which will be useful for aiding in the development of training aids for bomb-sniffing canines.

An electrospray chemical ionization source for real-time measurement of atmospheric organic and inorganic vapors

“…SESI-MS has been used for the real-time analysis of a variety of gas-phase analytes, including pharma- ceuticals (Wu et al, 2000;Meier et al, 2012), explosives (Tam and Hill et al, 2004;Aernecke et al, 2015), human metabolites (Martinez-Lozano et al, 2011;Garcia-Gomez et al, 2015), electronic cigarette vapors (Garcia-Gomez et al, 2016), volatile emissions from bacteria cultures (Zhu et al, 2010), food (Bean et al, 2015;Farrell et al, 2017), and plants ( . In SESI, the electrospray plume and incoming sample flow intersect in the ionization region, and analyte ionization proceeds likely via interactions with both small charged droplets and electrosprayproduced gas-phase reagent ions (Wu et al, 2000).…”

Molecular breath analysis supports altered amino acid metabolism in idiopathic pulmonary fibrosis

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Biomimetic Sniffing Improves the Detection Performance of a 3D Printed Nose of a Dog and a Commercial Trace Vapor Detector

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