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Rapid Detection of Explosive Vapors by Thermal Desorption - Atmospheric Pressure Photoionization - Differential Mobility Analysis - Tandem Mass Spectrometry.

RATIONALE
The increased frequency in the number of international terror threats has led to a corresponding increase in demand for fast, sensitive and reliable screening methods suitable for the detection of airborne explosive vapors. We demonstrate herein a workflow suitable for the determination of nitrogen-based explosives at the picogram level in just minutes.


METHODS
A method is described that combines Thermal Desorption (TD) sample introduction with Differential Mobility Analysis (DMA) - Tandem Mass Spectrometry (MS/MS), enabling a sensitive and accurate workflow suitable for the rapid detection of trace nitroaromatic, nitroester and nitramine explosive vapors. The methods are bridged using a novel low-flow, field-free Atmospheric Pressure Photoionization (APPI) source, intended specifically for the analysis of gas-phase analytes and airborne particles.


RESULTS
Limits of detection within or below the picogram range were determined for the analysis of a range of explosives standards including 2,6-DNT, TNT, TATB, Tetryl, RDX, EGDN, PETN, HMX, and NG. Practical application of the TD-APPI-DMA-MS/MS workflow was demonstrated for the detection of real trace explosive vapors produced from the volatilization of solid explosive samples stored within a sealed cardboard box. A single complete analysis was performed in less than two minutes.


CONCLUSIONS
The highly sensitive and accurate detection of a variety of common nitrogen-based explosive vapors has been demonstrated, at levels suitable for practical, high-throughput security screening applications.