Formation of organic chloramines during chlorination of 18 compounds

Organic chloramines have attracted considerable attention because of their potential toxicity and reactivity. However, the lack of suitable and effective analytical methods has limited the study of organic chloramines due to their volatile and unstable properties. In this study, membrane introduction mass spectrometry (MIMS) combined with DPD/FAS titration was used to monitor the formation of organic chloramines. N-chlorodimethylamine [(CH₃)₂NCl] and N-chlorodiethylamine [(C₂H₅)₂NCl] were detected and identified as the dominant volatile DBPs during chlorination of 18 organic compounds with dimethylamine or diethylamine functional groups, with yields ranging from 0.3% to 51.1% at a chlorine to precursor (Cl/P) molar ratio of 8.0. (CH₃)₂NBr was formed in the presence of bromide, while the formation of (CH₃)₂NCl was decreased. The reaction of phenol with (CH₃)₂NCl combined with theoretical calculations confirmed that the reactivity of (CH₃)₂NCl was similar to that of monochloramine. Moreover, (CH₃)₂NCl and (C₂H₅)₂NCl were observed at the ppb level during chlorination of actual water samples collected from different areas. The results suggest that (CH₃)₂NCl and (C₂H₅)₂NCl are important organic chloramines during chlorination, which may lead to the occurrence of further oxidation reactions and promote the formation of other disinfection byproducts simultaneously and should be of concern.