Laser-Based Techniques for the Detection of Cholorinated Aromatic Hydrocarbons

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Title Laser-Based Techniques for the Detection of Cholorinated Aromatic Hydrocarbons
Creator Rohlfing, Eric A.; Chandler, David W.; Fisk, George A.
Publisher Digitized by J. Willard Marriott Library, University of Utah
Date 1987
Spatial Coverage presented at Palm Springs, California
Abstract There is currently a need for a technique to detect chlorinated aromatics in the gas phase, for example in the exhaust stream of an incinerator. In this paper we present the results of our investigations into laser-based schemes that are ultrasensitive, species and isomer selective, and quasi-real time. Our approach is to use free-jet-expansion cooling to simplify greatly the UV absorption spectrum and to allow isomerically selective laser excitation of the frrst excited electronic state. This state is subsequently probed either by fluorescence (laser-induced fluorescence, or LIF) or photoionization (resonantly enhance multiphoton ionization, or REMPI). The photoions produced by REMPI are mass analyzed in a reflectron time-of-flight mass spectrometer (TOF MS) that has a resolution (M/6M) of -600 at mass 150. We shall discuss the application of these techniques to the mono- and dichlorinated benzenes and naphthalenes. For these species we have achieved ppb level detection limits with complete isomeric selectivity using a combination of the LIF and REMPI techniques. REMPI is more sensitive than LIF toward highly chlorinated aromatics that internally convert to the triplet state and have very small flourescent quantum yields. In addition, TOF MS provides a complete mass spectrum that can be used for additional identification and selectivity. Finally we address the applicability of these detection schemes to more complicated toxic species such as PCB's, dioxins, and furans and present ideas for a device that could be used for quasi-real-time detection in a typical working environment.
Type Text
Format application/pdf
Language eng
Rights This material may be protected by copyright. Permission required for use in any form. For further information please contact the American Flame Research Committee.
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ID 4357
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