title: Nitrogen oxides as dopants for the detection of aromatic compounds with ion mobility spectrometry.
abstract: Limits of detection (LODs) in ion mobility spectrometry (IMS) strictly depend on ionization of the analyte. Especially challenging is ionization of compounds with relatively low proton affinity (PA) such as aromatic compounds. To change the course of ion-molecule reactions and enhance the performance of the IMS spectrometer, substances called dopants are introduced into the carrier gas. In this work, we present the results of studies of detection using nitrogen oxides (NOx) dopants. Three aromatic compounds, benzene, toluene, toluene diisocyanate and, for comparison, two compounds with high PA, dimethyl methylphosphonate (DMMP) and triethyl phosphate (TEP), were selected as analytes. The influence of water vapour on these analyses was also studied. Experiments were carried out with a generator of gas mixtures that allowed for the simultaneous introduction of three substances into the carrier gas. The experiments showed that the use of NOxdopants significantly decreases LODs for aromatic compounds and does not affect the detection of compounds with high PA. The water vapour significantly disturbs the detection of aromatic compounds; however, doping with NOxallows to reduce the effect of humidity. Graphical Abstract Two possible ionization mechanisms of aromatic compounds in ion mobility spectrometry: proton transfer reaction and adduct formation.
authors.affiliation: Institute of Chemistry, Military University of Technology, Kaliskiego 2, 00-908, Warsaw, Poland.
authors.forename: Urszula
authors.initials: U
authors.lastname: Gaik
authors.affiliation: School of Engineering Science, Laboratory of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130, Mikkeli, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Sillanpää
authors.affiliation: Institute of Chemistry, Military University of Technology, Kaliskiego 2, 00-908, Warsaw, Poland.
authors.forename: Zygfryd
authors.initials: Z
authors.lastname: Witkiewicz
authors.affiliation: Institute of Chemistry, Military University of Technology, Kaliskiego 2, 00-908, Warsaw, Poland. jaroslaw.puton@wat.edu.pl.
authors.forename: Jarosław
authors.initials: J
authors.lastname: Puton
keywords: Aromatic compounds; Dopants; Ion mobility spectrometry; Nitrogen oxides