Development of a jet–REMPI (resonantly enhanced multiphoton ionization) continuous monitor for environmental applications

Abstract

The need for a continuous monitor for environmentally important pollutants at realistic [parts-per-trillion (parts in 10(12))] concentrations measured in real time (minutes) is widely recognized. We developed an instrument that is based on supersonic-jet expansion and cooling, followed by resonantly enhanced multiphoton ionization (REMPI) into a mass spectrometer. This approach furnishes the dual selectivity of narrow-band tuned laser absorption and mass analysis. We initiated a spectroscopic characterization of the jet's collisional cooling behavior to optimize the instrument's sensitivity and selectivity, made measurements of several aromatic compounds (including polychlorinated dioxins) by use of a one-color REMPI scheme, and demonstrated a two-color excitation scheme.

The Molecular Identification of Organic Compounds in the Atmosphere: State of the Art and Challenges

“…The most widely used is proton-transfer-reaction mass spectrometry, 105 where nearly all the organic gases present in air samples are ionized by accepting a proton from hydronium ions (H3O has increasingly been used in ambient atmosphere applications. 127 Aromatic compounds were investigated in the sub-ppb range applying jet-resonance-enhanced multiphoton ionization using a time-of-flight mass spectrometer downwind of a road. The Aerodyne Aerosol Mass Spectrometer (AMS) was developed for the on-line measurement of organic and inorganic components of aerosols.…”

Hydrocarbon detection using laser ion mobility spectrometry

“…Without employing adiabatic cooling the ionization excitation spectra, however, are relatively broad and featureless [25]. Selectivity can be improved by invoking the classical IMS criterion of ion drift time as a second selectivity feature.…”

Development of a Compact Supersonic Jet/Multiphoton Ionization/Time-of-Flight Mass Spectrometer for the On-site Analysis of Dioxin, Part I: Evaluation of Basic Performance

“…[6][7][8][9] In SSJ spectrometry, it is difficult to maintain a high vacuum, since a large quantity of the diluent gas expands into the vacuum. However, a flight tube that can be evacuated to below 10 -4 Pa is desirable, in order to avoid ion-molecule collisions which decrease the sensitivity.…”