Ultra-sensitive ambient ammonia detection using CO2-laser-based photoacoustic spectroscopy
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An ambient trace-ammonia sensor that uses resonant photoacoustic spectroscopy and a line-tunable CO2 laser has been developed. This system achieves a 1σ replicate precision of 32 parts-per-trillion (ppt) with an averaging time of 5 s and a total measurement time of 40 s. This 32-ppt precision corresponds to a minimum detectable fractional absorbance of 8.8×10-9, a minimum detectable absorption coefficient of 9.6×10-10 cm-1, and a minimum path-length-normalized detectivity of 1.1×10-8 W cm-1/Hz1/2. Background interference from CO2, H2O, and cell-window absorption were subtracted by switching to a neighboring off-resonance laser wavelength .
KeywordsSpectroscopy Ammonia Absorption Coefficient Measurement Time Laser Wavelength
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- 1.Guide for the Selection of Chemical Agent and Toxic Industrial Material Detection Equipment for Emergency First Responders (National Institute of Justice Guide 100–00, Vol. 1, 2000) Google Scholar
- 2.J.H. Seinfeld, S.N. Pandis: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change (John Wiley, New York 1998) Google Scholar
- 3.Ad Hoc Committee on Air Emissions from Animal Feeding Operations, Committee on Animal Nutrition, National Research Council: Air Emissions from Animal Feeding Operations: Current Knowledge, Future Needs, Final Report (2003) Google Scholar
- 4.Iowa State University and the University of Iowa Study Group: Iowa Concentrated Animal Feeding Operations Air Quality Study, Final Report (2002) Google Scholar
- 5.U.S. Environmental Protection Agency, Emission Standards Division, Office of Air Quality Planning and Standards: Emissions From Animal Feeding Operations, Draft Report, EPA Contract No. 68-D6–0011 (2001) Google Scholar
- 7.P. Hess (Ed.): Topics in Current Physics: Photoacoustic, Photothermal and Photochemical Processes in Gases (Springer-Verlag 1989) Google Scholar
- 17.Y.H. Pao (Ed.): Optoacoustic Spectroscopy and Detection (Academic Press, New York 1977) Google Scholar