Overlooked Formation of H2O2 during the Hydroxyl Radical-Scavenging Process When Using Alcohols as Scavengers

Hydroxyl radical (center dot OH) is an active species widely reported in studies across many scientific fields, and hence, its reliable analysis is vitally important. Currently, alcohols are commonly used as scavengers for center dot OH determination. However, the impacts of alcohols on the reliability of center dot OH detection remain unknown. In this study, we found that adding different types and different amounts of alcohols in water samples treated with ultraviolet irradiation undesirably produced substantial amounts of hydrogen peroxide (H2O2), which is a known center dot OH precursor. This means that the conventional center dot OH determination method using alcohols is likely unreliable or even misleading. Through careful investigation, we revealed an overlooked reaction pathway during H2O2 and center dot OH transformations. Varying oxygen concentrations, pHs, alcohol dosages, and types altered H2O2 formation, which can affect center dot OH determination accuracy. Among alcohols, n-butanol is the best scavenger because it quenches center dot OH rapidly but re-forms little H2O2.