Identification and quantification of chloramines, bromamines and bromochloramine by Membrane Introduction Mass Spectrometry (MIMS).

A Membrane Introduction Mass Spectrometry (MIMS) method was developed to differentiate and quantify the different chlorinated and brominated-amines, present in drinking water during chloramination. The representative mass to charge ratios (m/z) of 53, 85, 97, 175 and 131 corresponding to the mass of the parent compounds were selected to monitor NHCl, NHCl, NHBr, NHBr and NHBrCl and the detection limits were found to be 0.034, 0.034, 0.10, 0.12 and 0.36 mg/L as Cl, respectively. NHCl, NHBr and NHBrCl fragments interfere with the analysis/quantification of NHCl and NHBr via protonation reactions at hot metal surfaces inside the mass spectrometer. To accurately quantify NHCl or NHBr in mixtures of NHCl/NHCl or NHBr/NHBr, the interference from NHCl or NHBr was subtracted to the signal of the parent compound. If NHBrCl is present, NHBr and NHCl cannot be accurately quantified since the interference from the NHBrCl fragment cannot be distinguished from the signal of the parent compound. Under drinking water conditions, the interference from NHBrCl on NHCl was negligible. The different halamines were monitored and quantified for the first time in two surface waters and one seawater that were chloraminated to mimic a realistic disinfection scenario.