Real-time monitoring of the degradation of Cu(II)-EDTA in HO/UV using illumination-assisted droplet spray ionization mass spectrometry.

Illumination-assisted droplet spray ionization (IA-DSI) mass spectrometry was developed for in situ analysis and real-time monitoring of photolysis reactions. In IA-DSI, a photolysis reaction occurs on a corner of a cover slip positioned in front of a mass spectrometer, and the generated reaction intermediates are ionized via the corner and are directed to the inlet and analyzed by a mass spectrometer. IA-DSI is contaminant-free, low-cost and simple, and was demonstrated for in situ analysis and real-time monitoring of the degradation of Cu(II)-EDTA in HO/UV. The reaction times varied from seconds to minutes, and three new reaction intermediates were detected and identified by tandem mass spectrometry. More importantly, the proposed initiation site of Cu(II)-EDTA at the carboxyl group by ∙OH attack was verified for the first time. The degradation of Cu(II)-EDTA occurred through its chemical bonds broken at the carboxyl group, at the amino group, and between EDTA and Cu(II). By sampling in situ and monitoring in real time, IA-DSI provides advantages in simplifying the analysis process for photolysis reaction intermediates and products, and can detect photolysis reaction intermediates and products in less than a second.