Non-contact halogen lamp heating assisted LTP ionization miniature rectilinear ion trap: a platform for rapid, on-site explosives analysis

A platform consisting of a halogen lamp, a low temperature plasma (LTP) probe, and a miniature rectilinear ion trap mass spectrometer (RIT-MS) has been constructed and evaluated to detect organic and inorganic explosives on solid surfaces. This platform features two attractive characteristics: high sensitivity for the explosives with low volatility, and rapid analysis speed for the explosives on large surface areas. With non-contact heating by the halogen lamp, the signal intensities for the explosives with relatively high volatility were improved by over an order of magnitude, compared to those obtained at room temperature; and even more, the explosives with low volatility, which could hardly be detected at room temperature, were able to be readily identified. The limits of detection (LODs) of the selected explosives were all at the picogram level (e.g., 10 pg and 20 pg for TNT and RDX, respectively) with a heating time of 3 s. Using manual surface swabbing, the analysis of explosives on a large surface area (7.5 cm × 2.5 cm) was accomplished within 10 s, and an acceptable sensitivity could be acquired; additionally, inorganic explosives (black powder and firecracker) were successfully detected. Without any sample pretreatment, the platform was used to analyze the wastewater from an explosives factory, confirming the existence of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), and 2,6-dinitrotoluene (2,6-DNT), and the concentration of TNT was determined to be 5 ng mL−1. All these results indicated that the proposed platform was a promising technique for security monitoring and environmental analysis.