title: Secondary electrospray ionization (SESI) of ambient vapors for explosive detection at concentrations below parts per trillion.
abstract: We determine the sensitivity of several commercial atmospheric pressure ionization mass spectrometers towards ambient vapors, ionized by contact with an electrospray of acidified or ammoniated solvent, a technique often referred to as secondary electrospray ionization (SESI). Although a record limit of detection of 0.2 x 10(-12) atmospheres (0.2 ppt) is found for explosives such as PETN and 0.4 ppt for TNT (without preconcentration), this still implies the need for some 10(8)-10(9) vapor molecules/s for positive identification of explosives. This extremely inefficient use of sample is partly due to low charging probability ( approximately 10(-4)), finite ion transmission, and counting probability in the mass spectrometer (1/10 in quadrupoles), and a variable combination of duty cycle and background noise responsible typically for a 10(3) factor loss of useful signal.
authors.affiliation: Mechanical Engineering Department, Yale University, New Haven, CT, USA.
authors.forename: Pablo
authors.initials: P
authors.lastname: Martínez-Lozano
authors.forename: Juan
authors.initials: J
authors.lastname: Rus
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Fernández de la Mora
authors.forename: Marta
authors.initials: M
authors.lastname: Hernández
authors.forename: Juan
authors.initials: J
authors.lastname: Fernández de la Mora
mesh_terms: D001274:Atmospheric Pressure; D053834:Explosive Agents / Q000032:analysis*; D010417:Pentaerythritol Tetranitrate / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014303:Trinitrotoluene / Q000032:analysis; D035501:Uncertainty
chemical_list: D053834:Explosive Agents; D010417:Pentaerythritol Tetranitrate; D014303:Trinitrotoluene