title: Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization.
abstract: Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10-2s to 10-1s and Reynolds numbers on the order of 103to 104. The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m2area, 570 m3volume) was demonstrated for a 60-min period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 min of exposure.
authors.affiliation: National Institute of Standards and Technology, Materials Measurement Science Division, Gaithersburg, MD, USA. Electronic address: thomas.forbes@nist.gov.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Forbes
authors.affiliation: National Institute of Standards and Technology, Materials Measurement Science Division, Gaithersburg, MD, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Staymates
keywords: Aerodynamic reach; Explosives detection; Mass spectrometry; Remote sampling; Vapor and aerosol detection; Venturi-assisted entrainment