Ammonia monitoring at trace level using photoacoustic spectroscopy in industrial and environmental applications
An ammonia traces analyser based on photoacoustic spectroscopy is described. The system uses a CO2 laser and a properly designed resonant photoacoustic cell to achieve ammonia detection at sub-parts-per- billion (ppb) level. The instrument features unattended automatic on-line monitoring of ammonia with a detection limit of 0.1 ppb. Interferences from atmospheric CO2 and H2O are efficiently suppressed by a careful selection of the laser wavelength and a compensation of the water vapour signal made with a high-precision hygrometer. The cell design enables continuous measurement at high flow rates (up to 51/min), which guarantees a fast response time of the system for the monitoring of ammonia, a sticky polar molecule that adheres to most surfaces. Various examples of applications of the instrument in the semiconductor industry and for atmospheric pollution monitoring are presented. They demonstrate the excellent performances of the system and its suitability for these applications. © 2004 Elsevier B.V. All rights reserved.
Lab. of Nanophotonics and Metrology, Swiss Fed. Institute of Technology, CH-1015 Lausanne, Switzerland Compilation and indexing terms, Copyright 2008 Elsevier Inc. 04518721500 1386-1425 Ammonia monitoring CO2 laser Trace gas detection Environmental applications
Record created on 2008-09-29, modified on 2016-08-08