Liquid chromatography/electrospray ionisation sequential mass spectrometric identification of the main chlortoluron...

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.