A Kinetic Method for HO2•/O2•- Determination in Advanced Oxidation Processes

A new kinetic method is developed for the determination of hydroperoxyl radical (HO2•)/superoxide radical (O2•-) in aqueous solution, and the calibration using a kinetic half-life technique is also established for determining the concentration of HO2•/O2•- as produced in the UV/H2O2 process. This new method is based on the reduction of Fe3+−EDTA into Fe2+−EDTA by HO2•/O2•- and the well-known Fenton-like reaction of H2O2 and Fe2+−EDTA to yield the hydroxyl radicals (OH•). Benzoic acid scavenges the OH radicals to produce hydroxybenzoic acids, which are analyzed by fluorescence detection (λex = 320 nm; λem = 400 nm). The limit of detection for the new method depends on the pH values, and it is determined as 3.22 × 10-11 M with signal-to-noise ratio of 2 at pH 5. In addition, the present technique has the advantage of using inexpensive and easily available nonenzymatic reagents that do not require the specific instrument and chemicals and of being insensitive to the moderate concentration of possible interfe...