Rapid Detection and Quantification of DMNB Vapors Using a Handheld Ion Mobility Spectrometer Operated near Ambient Temperature

The detection of plastic explosives in vapor form is extremely challenging due to the very low volatility of their primary components, such as RDX and PETN. To overcome this limitation, volatile chemical markers like 2,3-dimethyl-2,3-dinitrobutane (DMNB) are added to explosive formulations to enable indirect vapor detection. This study presents a rapid method for detecting and quantifying DMNB vapors using a handheld ion mobility spectrometer (IMS) operating near ambient temperature, ammonia-doped and equipped with a non-radioactive corona discharge ionization source. The instrument, model LCD-3.2E (Smiths Detection Ltd.), is based on a twin drift–cell time-of-flight configuration and simultaneously records ion mobility spectra in both positive and negative modes. DMNB generated distinct product ion peaks in both modes, with reduced mobility values (K0) of 1.42 cm2·V−1·s−1 (positive) and 1.37 cm2·V−1·s−1 (negative). The method demonstrated high sensitivity, with limits of detection calculated at 1.4 ppbv (10.2 × 10−3 mg·m−3) in positive mode and 3.1 ppbv (22.7 × 10−3 mg·m−3) in negative mode. The IMS system provided rapid responses within seconds and covered a quantifiable concentration range of 5–3000 ppbv, with saturation estimated to appear above approximately 5 ppmv (36.6 mg·m−3). The simultaneous dual-polarity response of the DT IMS enhances both the selectivity and reliability of identification. These findings confirm the capability of portable IMSs for fast trace vapor detection in DMNB, supporting its application in field-based screening scenarios such as luggage inspection or container interrogation, where indirect detection of plastic explosives is required.