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.