Jet-REMPI for the Detection of Trace Gas Compounds in Complex Gas Mixtures, a Tool for Kinetic Research and Incinerator Process Control

Abstract

Flame optimization in incinerators is achievable by feedback control via kinetic modelling and on-line monitoring. On-line monitoring for process control requires a fast, selective and sensitive analytical device. In this paper a REM PI (Resonance Enhanced Multi Photon Ionization) mass spectrometer is presented which combines high sensitivity with very low cross-sensitivity. Consequently, it should be a valuable tool for both kinetic research and for on-line investigation. The sensitivity of the instrument has been increased by shifting the ionization regime close to the continuous portion ("jet") of the sample beam as opposed to the more conventional ionization within the molecular beam. A further gain in sensitivity was achieved by increasing the ionization volume which was made possible by a complete re-design of the ion source. A very low base-line level is achieved by using a geometry which prevents secondary ionization by the collision of ions/electrons with surfaces.These improvements result in an excellent performance from our apparatus which is demonstrated by the dichlorotoluene and naphthalene spectra which were obtained under a variety of conditions. For naphthalene we have now a detection limit of 5 ppt (mole fraction) for a SfN = I. Further developments of the technique are discussed.

Detection of Chlorobenzene Derivatives Using Vacuum Ultraviolet Ionization Time-of-Flight Mass Spectrometry

“…The resonance-enhanced multiphotonionization time-of-flight mass spectrometry (REMPI-TOFMS) technique has been used for the on-line measurement of chlorobenzenes. [2][3][4][5][6][7][8][9] Zimmermann et al [2][3][4][5][6] constructed mobile instruments for on-line monitoring of polyaromatic hydrocarbons and other aromatic species in the flue gas of industrial incineration plants. also performed REMPI mass spectrometry to detect chlorinated aromatic compounds.…”

Development of medium pressure laser ionization, MPLI. Description of the MPLI ion source

“…Additionally, a detection limit of 12 pptV with an integration time of 10 s for 2,5-DCT has been achieved with MPLI, which is considerably lower than the value of 100 pptV reported by Oser et al [9]. In their experiments, a 10 mm 3 ionization volume and an integration time of 20 seconds was used.…”

“…Typical pulse durations, observed at 50% intensity, are ϳ11 ns for the tunable radiation and ϳ25 ns for the radiation emitted directly from the excimer laser. Pump and ionization laser pulses were synchronized with a four channel Stanford DG 505 (Stanford, Sunnyvale, CA) [9]. The redesigned ion source geometry allows for significant reduction of the nozzle/ skimmer distance in an orthogonal beam geometry.…”

Use of Ring-Repeller, Double-Skimmer Electrodes for Efficient Ion Focusing in Mass Spectrometry

“…It should be noted in this respect that Oser et al used a skimmer for the separation of ionization and ion-acceleration regions. 11 In the proximity ionization scheme, the laser beam is proposed to be line-focused in a jet to form a disk-like ionization region, which is suitable for improving both the ionization efficiency and the mass resolution. A new type of electrode assembly is desirable to properly focus the ion spread in the disk-like volume and to avoid the introduction of neutral expanded gas into the drift region.…”

“…It should be noted that a portion of the ions is accelerated toward the chamber surface, since the potential of the chamber is 0 V. Oser and co-workers applied -2000 V to the skimmer electrode, and, under these conditions, the ions were found to be efficiently extracted into the skimmer. 11 In this case, the potential of the flight tube, unfortunately, becomes -2000 V, since the difference in the potential between the skimmer and the drift tube should be zero.…”