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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 29, Number 4
BKCSDE 29(4)
April 20, 2008 

 
Title
In-situ Calibration of the Hydroperoxyl Radical Using an Immobilized
TiO2 Photocatalyst in the Atmosphere
Author
Bum Gun Kwon
Keywords
Hydroperoxyl radical, In-situ calibration, TiO2, Kinetic method
Abstract
The present study is the first report of utilizing TiO2 photocatalyst to analytically calibrate the hydroperoxyl radical (HO2·). An in-situ calibration method of HO2· is proposed for air monitoring by using an 2-methyl-6-(p-methoxyphenyl)- 3,7-dihydroimidazo-[1,2-a]pyrazin-3-one (MCLA)-chemiluminescence (CL) technique. In this method, HO2· (pKa = 4.80) is produced by the ultraviolet (UV) photolysis of immobilized TiO2 using a constant flow rate of air equilibrated water, in which HO2· is controlled by using various lengths of knotted tubing reactor (KTR). The principle of the proposed calibration is based on the experimentally determined halflife (t1/2) of HO2· and its empirically observed pH-dependent rate constant, kobs, at a given pH. The concentration of HO2·/O2·? is increased as pH increases. This pH dependence is due to the different disproportionative reactivities between HO2·/O2·? and HO2·/O2·?. Experimental results indicate the practical feasibility of the approach, producing very promising method.
Page
785 - 789
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