TITLE

Modification of a commercial cavity ring-down spectroscopy NO2 detector for enhanced sensitivity

AUTHOR(S)
Castellanos, Patricia; Luke, Winston T.; Kelley, Paul; Stehr, Jeffrey W.; Ehrman, Sheryl H.; Dickerson, Russell R.
PUB. DATE
November 2009
SOURCE
Review of Scientific Instruments;Nov2009, Vol. 80 Issue 11, p113107
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Nitrogen dioxide (NO2) plays a central role in atmospheric chemistry, air pollution, and biogeochemical cycles. Many analytical techniques have been developed to detect NO2, but only chemiluminescence-based instruments are commonly, commercially available. There remains a need for a fast, light, and simple method to directly measure NO2. In this work we describe the modification and characterization of a small, commercially available cavity ring-down spectroscopy (CRDS) NO2 detector suitable for surface and aircraft monitoring. A metal oxide scrubber was added to remove NO2, and provide a chemical zero, improving the detection limit (3σ of the background noise) from several parts per billion by volume (ppbv) to 0.06 ppbv, integrated over 60 s. Known interferences by water and particles were removed using Nafion tubing and a 1 μm Teflon® filter, respectively. A 95% response time of 18±1 s was observed for a step change in concentration. The CRDS detector was run in parallel to an ozone chemiluminescence device with photolytic conversion of NO2 to NO. The two instruments measured ambient air in suburban Maryland. A least-squares fit to the comparison data resulted a slope of 0.960±0.002 and R of 0.995, showing agreement within experimental uncertainty.
ACCESSION #
45515515

 

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