Liquid chromatography/electrospray ionisation sequential mass spectrometric identification of the main chlortoluron by-products during water disinfection using chlorine

Abstract

The main degradation by-products of the herbicide chlortoluron formed during water disinfection with HOCl/ClO(-) have been separated and identified by liquid chromatography/electrospray ionisation sequential mass spectrometry (LC/ESI-MS(n)). Chlorination and hydroxylation reactions seem to occur exclusively on the aromatic ring of chlortoluron, leading to by-products which show characteristic fragmentation patterns. Indeed, chlortoluron-like ESI spectra were always observed for chlorinated by-products, showing only a fragment at m/z 72. In contrast, hydroxylated and chloro/hydroxylated by-products gave a much more complex fragmentation pattern that could be elucidated by MS(n) (n = 1-4) experiments. A mechanistic scheme rationalising the observed fragmentation pattern is proposed and discussed. Copyright 2000 John Wiley & Sons, Ltd.

Photocatalytic degradation of phenyl‐urea herbicides chlortoluron and chloroxuron: characterization of the by‐products by liquid chromatography coupled to electrospray ionization tandem mass spectrometry

“…4. In particular, the structure proposed in the case of 229A is the same as that reported for the corresponding product ion arising from the [M+H] + ion of a hydroxy derivative of chlortoluron found during chemical (hypochloride) degradation 9, 10. Indeed, the MS/MS spectrum of the latter is identical to that of 229A, both also showing product ions at m/z 184 and 193.…”

“…The latter was dramatically confirmed by some specific cases of severe contamination (see, for example, the temporary closure of a water intake in the Isle of Wight, UK, in 1994, due to the high levels of the phenyl‐urea herbicides isoproturon and chlortoluron 6). The risk to human health arising from water contamination by phenyl‐urea herbicides is increased by the consideration that their by‐products generated during water disinfection processes based on oxidants like chlorine (hypochlorite) or ozone7–10 could be more toxic than the herbicides themselves.…”

Photocatalytic degradation of the herbicide isoproturon: characterisation of by‐products by liquid chromatography with electrospray ionisation tandem mass spectrometry

“…The generation of these compounds could be easily predicted, since they have been already observed in other degradation processes of phenylurea pesticides involving OH . radicals 13–16. Less intense peaks were observed for ions at m/z 255, corresponding to trihydroxylated derivatives of isoproturon.…”

Identification of disinfection by‐products of selected triazines in drinking water by LC‐Q‐ToF‐MS/MS and evaluation of their toxicity

“…Sodium hypochlorite (NaClO) is one of the most used disinfectants worldwide,7 underlining the importance of identifying possible degradation products resulting from this procedure. In the disinfection process, hypochlorous acid (HClO) is the main responsible reagent for pathogen destruction, but both HClO and ClO − react with organic compounds giving addition, substitution, or oxidation products 8. A further interesting fact is that while chlorinated, s‐triazines do not react with chlorine, the non‐chlorinated s‐triazines react very quickly with this compound 9…”