Selective Detection of Carbon-Centered Radicals in Water via a Fluorescent Probe and High-Resolution Mass Spectrometry

Carbon-centered radicals (CCRs) are key intermediates in the transformation of organic contaminants in aquatic environments. This study developed a robust workflow using a fluorescent probe coupled with high-resolution mass spectrometry (HRMS) to identify CCRs in aquatic environments. Nine fluorescent probes were systematically evaluated, with 3-ap/BDP selected as the optimal probe due to its superior performance in detecting a wide range of model CCRs. The method demonstrated excellent linearity, minimal matrix interference, and high sensitivity, enabling the detection of CCRs at trace concentrations in complex environmental matrices. The workflow was applied to analyze CCRs generated in natural organic matter under solar irradiation and advanced oxidation processes (AOPs). A total of 30 CCRs were identified, with distinct profiles observed between solar-irradiated and AOP-treated samples. Solar irradiation favored the formation of CCRs with higher m/z values, while AOPs generated CCRs with lower m/z values, highlighting the influence of reactive species on CCR formation. These findings provide critical insights into the environmental behavior of CCRs in aquatic environments. Moreover, the developed workflow offers a powerful tool for monitoring CCRs in natural and engineered water systems. .