Geometry-independent neutral desorption device for the sensitive EESI-MSdetection of explosives on various surfaces

摘要

A novel geometry-independent neutral desorption (GIND) device was successfully developed, whichnmade neutral desorption (ND) sampling easier and more robust on virtually all types of surfaces. ThenGIND device features a small air-tight enclosure with fixed space between the ND gas emitter, thensample surface, and the sample collector. Besides easy fabrication and convenient use, thisnconfiguration facilitates efficient neutral sample transfer and results in high sensitivity by preventingnmaterial loss during the ND process. The effects of various operating parameters of the GIND devicensuch as desorption gas composition, surface wetness, gas flow rate, distance between the surface and thengas emitter, internal diameter of the sample outlet, and GIND device material were experimentallyninvestigated. By using the GIND device, trace amounts of typical explosives such as TNT, RDX,nHMX, TATP, etc., were successfully sampled from many different kinds of surfaces, including humannskin, glove, glass, envelope, plastic, leather, glass, and clothes. GIND-sampled explosives were detectednby multiple-stage extractive electrospray ionization mass spectrometry (EESI-MS). Ion/moleculenreactions of explosives such as RDX and TATP were implemented in the EESI source for the rapidndetection with enhanced sensitivity and specificity. The typical time for a single sample analysis wasna few seconds. Successful transportation of the neutral analytes over a distance longer than 10 m wasndemonstrated, without either significant signal loss or serious delay of signal response. The limit ofndetection for these explosives in the study was in the range of ca. 59–842 fg (S/N ¼ 3, n ¼ 8) on variousnsurfaces. Acceptable relative standard deviation (RSD) values (ca. 4.6–10.2%, n ¼ 8) were obtained fornall the surfaces tested, showing the successful sampling of trace non-volatile explosive compoundsn(sub-picogram) by the GIND device for the EESI mass spectrometric analysis.