An Advanced Kinetic Method for HO_2·/O_2~-· Determination by Using Terephthalate in the Aqueous Solution

摘要

Hydroperoxyl radical/superoxide anion radical (HO_2·/O_2~-?, pK_a = 4.8) as an intermediate is of considerable importance in oxidation processes. Hence, the method of detecting HO_2 /O_2~- ? with high sensitivity is necessary to be developed. To achieve this objective, this study newly employed terephthalate (TA) as a probe for the measurement of HO_2·/O_2~- · in the kinetic method presented in our previous study. This method was based on the hydroxylation of TA to produce mainly hydroxyterephthalic acid or hydroxyterephthalate (OHTA), which was analyzed by fluorescence detection (λ_(ex) = 315 nm, λ_(em) = 425 nm). The life-time of HO_2· /O_2~- · and its concentration formed from the photolysis technique of H_2O_2 were reported in this study. At range of pH 2-10, the life-time of HO_2·/O_2~- ? was 51-422 sec. In particular, an increase in the life-time with pH was observed. The sensitivities of the kinetic method by using TA were always higher with 1.7-2.5 times at pH 8.0 than those by using benzoic acid. From these results, this study can contribute to understanding the basic functions of HO_2·/O_2~- ? in oxidation processes.