Droplet spray ionization mass spectrometry for real-time monitoring of activation of peroxymonosulfate by 1,4-benzoquinone

The mechanism of activation of peroxymonosulfate (PMS) by 1,4-benzoquinone (p-BQ) was investigated. Droplet spray ionization mass spectrometry (DSI-MS) was used for in situ analysis and real-time monitoring of this reaction. DSI-MS can eliminate the detecting delay caused by the multiple handing steps such as dilution, filtration and extraction. This has the further benefit for real-time detection of reactive intermediates. Different from persulfate activated by quinones, PMS was activated by p-BQwith the generation of singlet oxygen (0;(singlet)) instead of hydroxyl radical (center dot OH) and sulfate radical (SO4 center dot(-)). The O-2* (singlet) was chemically trapped by using 9,10-diphenylanthracene as a chemical probe. The generated intermediates during activation of PMS by p-BQ were detected and characterized by DSI-MS in real time. A possible mechanism about O-2*(singlet) evolution involving peroxide adducts as well as dioxirane intermediates was confirmed accordingly. Using the DSI-MS to study the activation of PMS by O-18-labeled p-BQfurther confirmed the 0;(singlet) evolution. The results suggest that DSI-MS has advantages of characterizing the reactive intermediates that generated in the PMS/p-BQ process. It is thus a potential tool to trace the reaction process, to detect reactive intermediates, and to study reaction mechanism in advanced oxidation processes (AOPs). (C) 2018 Elsevier B.V. All rights reserved.