Part per quadrillion quantitation of pentaerythritol tetranitrate vapor using online sampling gas chromatography–mass spectrometry

Development of a Gas Chromatography with High-Resolution Time-of-Flight Mass Spectrometry Methodology for BDNPA/F

Analysis of thermally labile compounds such as bis(2,2-dinitropropyl) acetal/formal (BDNPA/F), an energetic plasticizer, is usually performed via liquid chromatography (LC) as opposed to gas chromatography (GC) due to thermal decomposition in the inlet or the analytical column. While LC is a powerful technique, the analysis of volatile and semivolatile compounds is best suited to GC. Herein, a method was developed for a gas chromatograph coupled to high-resolution mass spectrometer (GC-HRMS), utilizing a programmable temperature vaporizer (PTV) inlet. A subset of the native compounds and several produced by the thermal decomposition of BDNPA/F in the inlet were evaluated by using multiple PTV inlet parameters to determine the optimal ramp rate and final temperature of the inlet (60 °C/min from 60 to 325 °C). The optimized GC-HRMS method nearly reduced all thermal decomposition, allowing for an excellent separation to be obtained. Furthermore, multiple ionization methods, including electron impact (EI), negative chemical ionization (NCI), and positive chemical ionization (PCI), were used to explore the many chemical differences between the BDNPA/F samples. A preliminary investigation of the benefits of using GC-HRMS to evaluate the chemical differences between unaged and aged BDNPA/F samples for unique insight was evaluated.

Empirical determination of explosive vapor transport efficiencies

The transport efficiency of 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazinane (RDX) trace vapors through tubing materials that commonly constitute vapor handling infrastructures have been determined for a variety of tubing dimensions and sampling conditions. Using a programmable temperature vaporization inlet coupled with a gas chromatography mass spectrometer (PTV-GC-MS), the explosive vapors were quantified both with and without a length of tubing of a specific material in the sampling flow path. At vapor temperatures of 30 °C and 66 °C, minimal attenuations were observed for 2,4-DNT and TNT vapor concentrations when the tubing material was in-line with the sampling flow path, indicating that the transport is largely unaffected by interactions with the surface of the tubing materials. In contrast, RDX vapors showed large attenuations as a function of both sampling conditions and tubing materials/dimensions. For those experiments where attenuated RDX vapor transport was observed, the mass sequestered by interactions between the flowing vapor and the internal tubing surface was determined to be in the range of tens to hundreds of picograms. Of all the materials examined for RDX transport, fluorinated ethylene propylene (FEP) tubing resulted in the least amount of mass loss to surface interactions, with vapor transport efficiencies (VTEs) between 95-100%. However, for some materials, the combination of tubing dimensions and sampling conditions resulted in no RDX transport, even after sampling more than 250.0 L of vapor through the tubing.