Interference of dissolved organic matter and its constituents on the accurate determination of hydrogen peroxide in water.

Hydrogen peroxide (HO) is ubiquitous in natural waters, and plays an important role in both biological and chemical processes. This study investigated the influence of dissolved organic matter (DOM) and its substituents on the accurate measurement of HO by peroxidase-mediated depletion of scopoletin fluorescence method which is one of the most widely used methods for the determination of low concentration HO in water. Six DOM and its 24 substituents interfered the determination of HO at environmentally relevant concentration of 200 nM with different levels except 2,6-dimethoxy-1,4-benzoquinone and benzoic acid, which may be associated with origin and types of DOM, and numbers and position of active functional groups in DOM constituents. Each substance concentration and the corresponding decreasing ratio to the measured HO concentration was fitted well to the linear model (R > 0.9), and the obtained interfering ratios (k, (mgC L)), expressing the degree of DOM or its substituents per unit concentration to the measurement of HO, were approximate for DOM, but the order of magnitude of k values of DOM constituents took on a large span from 10 to 10. When DOM levels exceed 0.1 mgC L or its substituent concentration is at nM level (low to 20 nM), the HO content will be underestimated substantially. A quantitative structure-activity relationship model with remarkable stability and strong predictability for the k of DOM substituents to HO measurement was established, and the k was related to the electron transfer capacity, hydrophobicity and stability of these compounds.