Analytical Sciences

Nanomolar Determination of Hydrogen Peroxide in Coastal Seawater Based on the Fenton Reaction with Terephthalate

Kazuhiko TAKEDA,*,** Hitoshi NOJIMA,* Kengo KUWAHARA,** Russel Chrispine CHIDYA,* Adeniyi Olufemi ADESINA,* and Hiroshi SAKUGAWA*,**

*Graduate School of Biosphere Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan
**Faculty of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan

A non-enzymatic fluorescence method for the determination of hydrogen peroxide (H₂O₂) was investigated. This method is based on the hydroxylation reaction of terephthalate (TP) by hydroxyl radical formed from reaction between H₂O₂ and Fe(II), resulting in the formation of a strongly fluorescent 2-hydroxyterephthalate (HTP). Under optimized conditions, a 3 nM detection limit and 1.0% precision at 200 nM were obtained. This was sensitive enough to determine the concentrations of H₂O₂ in coastal marine environments. The slopes of the calibration curve in seawater were nearly the same as those in Milli-Q water, suggesting that the fluorescent intensity was not affected by coexisting sea salts. However, the presence of nitrite at more than 10 μM interfered with the formation of HTP. The developed method was successfully applied to determine the concentrations of H₂O₂ in Osaka Bay on the research vessel. The results obtained in Osaka Bay demonstrated that H₂O₂ was photochemically produced via the photolysis of dissolved organic matter supplied from the river with fresh water at the surface layer.

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