Detection of explosives in vapor phase by field asymmetric ion mobility spectrometry with dopant-assisted laser ionization.

Detection of low-volatile explosives in concentrations below 10 g/cm is a great challenge for portable ion mobility spectrometers (IMS) and field asymmetric IMS (FAIMS). We study the capabilities of FAIMS detector with ultraviolet laser ionization combined with organic additives (dopants) toluene and 1-methylnaphtalene to sense nitro-explosives: trinitrotoluene (TNT) and low-volatile cyclonite (RDX) and nitropentaerythritol (PETN). Differential mobility coefficients were measured for target ion peaks of TNT, RDX and PETN. Presence of dopants in the sample results in multiple growth of ion yield at laser intensities lower than 2 × 10 W/cm. Limits of detection with dopant-assisted laser ionization were determined: 4.7 × 10 g/cm for RDX and 9.8 × 10 g/cm for PETN. Obtained results propose a way to further improve sensitivity of detectors along with improvement of portability of current laser-based FAIMS prototypes by using less powerful and smaller lasers.