Spectrophotometric determination of hydrogen peroxide in water with peroxidase-catalyzed oxidation of potassium iodide and its applications to hydroxylamine-involved Fenton and Fenton-like systems.

A spectrophotometric method for the rapid measurement of hydrogen peroxide (HO) in aqueous solutions was developed in this study. This method is based on a reaction catalyzed by peroxidase (POD) in which potassium iodide (KI) is oxidized to generate the stable yellow-colored I within 15 s. The absorbance of the generated I at both 350 nm and 400 nm had good linear relationships with HO concentration in the range of 0-70 μM (R > 0.999) with sensitivities of 2.34 × 10 M cm and 5.30 × 10 M cm respectively. Meanwhile, through calculation, the detection limits of the proposed POD-KI method at 350 nm and 400 nm were 0.09 μM and 0.33 μM, respectively. Even when the concentration of HO was up to 350 μM, the absorbance of the generated I at 350 nm did not decrease observably. The generated I was found to be stable enough in ultrapure water, underground water, reservoir water and samples containing the strong reducing agent hydroxylamine. Moreover, the proposed POD-KI method was successfully used to analyze trace HO in rainwater, and to monitor the change of HO concentration in the Fenton, hydroxylamine/Fenton and hydroxylamine/Cu(II)/HO systems. Overall, the POD-KI method could be adopted as a candidate method to determine HO in Fenton and Fenton-like systems, and especially in those involving hydroxylamine.