Online chemiluminescence determination of the hydroxyl radical using coumarin as a probe

The hydroxyl radical (˙OH) is one of the strongest oxidizing species, which can react with a variety of organic and inorganic chemicals. Although ˙OH is widely used for degradation of environmental pollutants, detection of ˙OH remains a major challenge due to its high reactivity and short lifetime, especially online detection. In this study, a novel method for online detection of ˙OH by flow oxidization chemiluminescence (F-OCL) using coumarin as a probe was established. The concentrations of ˙OH determined by this new method were consistent with those determined by HPLC analysis. Because the new method has a short response speed, it was successfully used to quantify the dynamic change of ˙OH in the TiO2 photocatalytic process and Fenton reaction in real time. Furthermore, a combination of two chemiluminescence systems was developed to track the dynamics of ˙OH and hydrogen peroxide (H2O2) in homogeneous or heterogeneous Fenton reactions occurring in soil slurry. The proposed method and strategy have good application potential in online ROS monitoring of both natural and engineered systems.