In-situ Calibration of the Hydroperoxyl Radical Using an Immobilized TiO 2 Photocatalyst in the Atmosphere

The present study is the first report of utilizing TiO 2 photocatalyst to analytically calibrate the hydroperoxyl radical (HO 2 . ). An in-situ calibration method of HO 2 . 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, HO 2 . (pK a = 4.80) is produced by the ultraviolet (UV) photolysis of immobilized TiO 2 using a constant flow rate of air equilibrated water, in which HO 2 is controlled by using various lengths of knotted tubing reactor (KTR). The principle of the proposed calibration is based on the experimentally determined half-life (t 1/2 ) of HO 2 . and its empirically observed pH-dependent rate constant, k obs , at a given pH. The concentration of HO 2 . /O 2 .- is increased as pH increases. This pH dependence is due to the different disproportionative reactivities between HO 2 . /O 2 .- and HO 2 . /O 2 .- . Experimental results indicate the practical feasibility of the approach, producing very promising method.

[1]  O. Shimomura,et al.  Evaluation of five imidazopyrazinone-type chemiluminescent superoxide probes and their application to the measurement of superoxide anion generated by Listeria monocytogenes. , 1998, Analytical biochemistry.

[2]  Andrew Mills,et al.  An overview of semiconductor photocatalysis , 1997 .

[3]  J. Yates,et al.  Photocatalysis on TiO2 Surfaces: Principles, Mechanisms, and Selected Results , 1995 .

[4]  Y. Nosaka,et al.  Properties of O2.- and OH. formed in TiO2 aqueous suspensions by photocatalytic reaction and the influence of H2O2 and some ions , 2002 .

[5]  S. Martin,et al.  Environmental Applications of Semiconductor Photocatalysis , 1995 .

[6]  B. Ohtani,et al.  Mechanism of photocatalytic production of active oxygens on highly crystalline TiO2 particles by means of chemiluminescent probing and ESR spectroscopy , 2001 .

[7]  Correction to ``Effect of peroxy radical reactions on the predicted concentrations of ozone, nitrogenous compounds, and radicals'' , 1996 .

[8]  M. Grätzel,et al.  EPR study of hydrated anatase under UV irradiation , 1987 .

[9]  Robert J. O'Brien,et al.  Tropospheric free radical determination by FAGE , 1984 .

[10]  A. Heller,et al.  Palladium catalysis of O2 reduction by electrons accumulated on TiO2 particles during photoassisted oxidation of organic compounds , 1992 .

[11]  O. Shimomura,et al.  Coelenterazine analogs as chemiluminescent probe for superoxide anion. , 1997, Analytical biochemistry.

[12]  S. Springston,et al.  Quantitative analysis of hydroperoxyl radical using flow injection analysis with chemiluminescence detection. , 2003, Analytical chemistry.

[13]  D. Ollis,et al.  Simple Photocatalysis Model for Photoefficiency Enhancement via Controlled, Periodic Illumination , 1997 .

[14]  Y. Nosaka,et al.  Application of Chemiluminescent Probe to Monitoring Superoxide Radicals and Hydrogen Peroxide in TiO2 Photocatalysis , 1997 .

[15]  C. Cantrell,et al.  Dual-inlet chemical amplifier for atmospheric peroxy radical measurements. , 1996, Analytical chemistry.

[16]  M. Nakano,et al.  Chemiluminescence probe with Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-a]pyrazin-3-one, for estimating the ability of human granulocytes to generate O2-. , 1986, Analytical biochemistry.

[17]  Atmospheric ROx Radicals at an Urban Site: Comparison to a Simple Theoretical Model. , 1995, Environmental science & technology.

[18]  Yongfa Zhu,et al.  The synthesis of nanosized TiO2 powder using a sol-gel method with TiCl4 as a precursor , 2000 .

[19]  P. Pichat,et al.  Study of oxygen isotopic exchange over ultraviolet irradiated anatase samples and comparison with the photooxidation of isobutane into acetone , 1977 .

[20]  S. Sillman,et al.  Model correlations for ozone, reactive nitrogen, and peroxides for Nashville in comparison with measurements : Implications for O3-NOx-hydrocarbon chemistry , 1998 .

[21]  B. Kwon,et al.  A kinetic method for HO2*/O2*- determination in advanced oxidation processes. , 2004, Analytical chemistry.

[22]  William H. Brune,et al.  Measurement of tropospheric OH and HO2 by laser‐induced fluorescence at low pressure , 1994 .

[23]  G. W. Harris,et al.  Calibrated chemical amplifier for atmospheric ROx measurements , 1991 .

[24]  D. Stedman,et al.  A possible technique for the measurement of atmospheric peroxy radicals , 1982 .

[25]  M. Pilling,et al.  Measurement of OH and HO2 in the troposphere. , 2003, Chemical reviews.

[26]  A. Heller,et al.  The role of oxygen in photooxidation of organic molecules on semiconductor particles , 1991 .