Abstract
A simple and sensitive method based on a liquid droplet is described for the measurement of atmospheric ozone. A 30 µL drop of indigo blue solution is suspended in a flowing-air sampling stream. The ozone collected reacts with the indigo solution resulting in its decolorization. The colorimetric sensor is composed of two optical fibers and the source of monochromatic light was a red LED (625 nm). The calibration curve was constructed with ozone standard concentrations ranging from 37 - 123 ppbv. The detection limit achieved was 7.3 ppbv. The method considered here showed itself to be easy to apply with a fast response and a total analysis time of only 5 minutes.
Highlights
Photolysis of ozone at wavelengths < 319 nm is important as the main source of hydroxyl radical (OH), which largely determines the oxidative capacity of the lower atmosphere.[4,5,6,7]
The position of the optical fibers OF1,2 relative to Teflon tube T2 determines the manner in which the droplet is probed by the source beam, and affects the detection sensitivity
When the optical fibers OF1,2 and the Teflon tube T2 were positioned with h= 3.0 mm and d= 7.5 mm, the best analytical signal was obtained and the sensor gave the highest difference between the analytical signals measured using water and indigo blue solution
Summary
Ambient ozone, produced during NO2 photolysis at wavelengths < 400 nm, is a common urban and regional air pollution problem in many parts of the world.[1,2,3] Photolysis of ozone at wavelengths < 319 nm is important as the main source of hydroxyl radical (OH), which largely determines the oxidative capacity of the lower atmosphere.[4,5,6,7] When present at high concentrations ozone can cause a range of adverse environmental impacts on human health, crops, natural vegetation and outdoor materials.[8,9,10,11,12] Concentrations of background ozone appear to have been increasing since the industrial revolution. When the optical fibers OF1,2 and the Teflon tube T2 were positioned with h= 3.0 mm and d= 7.5 mm, the best analytical signal was obtained and the sensor gave the highest difference between the analytical signals measured using water and indigo blue solution.
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