MEASUREMENTS OF PEROXY RADICALS USING CHEMICAL AMPLIFICATION/CAVITY RING-DOWN SPECTROSCOPY
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Publisher:Ohio State University
The peroxy radical chemical amplification (PERCA) method is combined with cavity ring-down spectroscopy (CRDS) to measure peroxy radicals HO$_2$ and RO$_2$. HO$_2$ and RO$_2$ are converted to NO$_2$ via reactions with NO, with subsequent reactions to recycle most of the OH and RO coproducts back to HO$_2$ by reactions with CO and O$_2$ and amplify the level of NO$_2$. The amplified NO$_2$ is then monitored by CRDS, a sensitive absorption technique. The PERCA-CRDS method is calibrated with a HO$_2$ radical source (0.5-3 ppb); using a 3-meter Teflon tubing as the reactor and 2.5 ppmv NO and 5\% vol/vol CO, the PERCA amplification factor or chain length is determined to be 150 +-50 in this study. The peroxy radical detection sensitivity by PERCA-CRDS is approx. 5 pptv/30s. Ambient measurements of the peroxy radicals are carried out at Riverside, California in 2007 to demonstrate the PERCA-CRDS method.
Author Institution: Department of Chemistry, University of California, Riverside, CA 92521; Instituto de Quimica, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, 04510, Mexico, D.F., Mexico; Department of Chemistry, University of California, Riverside, CA 92521; Department of Chemistry and Air Pollution Research Center, University of California, Riverside, CA 92521
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