Challenges and opportunities for on-line monitoring of chlorine-produced oxidants in seawater using portable membrane-introduction Fourier transform-ion cyclotron resonance mass spectrometry.

The present study reports the first evaluation of a MIMS device equipped with a high-resolution Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS) for comprehensive speciation of chlorine-produced oxidants (CPO) in seawater. A total of 40 model compounds were studied: 4 inorganic haloamines (mono-, di-, and trichloramine and monobromamine), 22 organic N-haloamines, 12 N-haloamino acids, and 2 free oxidants (HOCl/ClO and HOBr/BrO). The main key factors influencing the analytes' introduction and their detection were optimized. Under optimized conditions, the rise and fall times of the MIMS signal ranged from 8 to 79 min and from 7 to 73 min, respectively, depending on the compound. Free oxidants and N-haloamino acids, which are ionic or too polar at seawater pH, hardly crossed the membrane, and MIMS analysis was thus unsuitable. Nevertheless, better enrichment and therefore better sensitivity were achieved with organic N-haloamines than with inorganic haloamines. The observed detection limits ranged from tens of μM to sub-μM levels. Oxidant decomposition occurred inside the MIMS device, at a higher rate for N-bromamines than for chlorinated analogues.Graphical abstract.