Analytical Sciences

A Calibration Method for Measurement of Small Alkyl Organic Peroxy Radicals by Chemical Amplifier

Bin QI,* Akinori TAKAMI,** and Shiro HATAKEYAMA**

*School of Chemistry and Material Sciences, Shaanxi Normal University, Xian 710062, China
**National Institute of Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan

A new method is proposed to determine the calibration factor (CF) of methyl and ethyl peroxy radicals in a chemical amplifier. The radical source comes from the reactions of excess methane and ethane, respectively, with known concentrations of OH radicals generated by the photolysis of water vapor at 184.9 nm in air in a flow tube. This yields a mixed radical source with equal amounts of HO₂ and RO₂ (R = CH₃, C₂H₅). The CF for RO₂ can be derived from the CF for HO₂ and an average CF for the mixed radicals. The reliability of the method was evaluated by comparing the CF ratios of RO₂ to HO₂ obtained from both the experiments and theoretical calculations.

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