On-line monitoring of photolysis reactions using electrospray ionization mass spectrometry coupled with pressurized photoreactor

A simple method by coupling a spray capillary with pressurized photoreactor for on-line monitoring of photolysis reactions was reported. In this method, only an inert gas is used to transfer the reaction solution, which avoids potential sample loss and contamination. The photolysis reaction is online quenched, and therefore, it has advantages of on-line detection and characterization of photolysis reaction intermediates. The assembly is easy to achieve, low-cost, and robust. Different from off-line methods, the photolysis reaction solution is directly transferred to a capillary tip for ionization, avoiding the delay in the detection of reactive intermediates. With this setup, this technique has been applied for on-line monitoring of degradation of cyclophosphamide (CP) in H₂O₂/UV for which two new intermediates were intercepted and structurally characterized for the first time by tandem mass spectrometry. In H₂O₂/UV, the degradation of CP occurred via hydroxylation, dehydrogenation, chlorine substitution reaction, and cleavage of the chloroethyl group. These results indicate that the coupling of electrospray ionization mass spectrometry with pressurized photoreactor can detect and characterize the key photolysis reaction intermediates, which render it a potential tool for elucidating the mechanism of water remediation.