Aquatic degradation of triclosan and formation of toxic chlorophenols in presence of low concentrations of free chlorine
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The degradation of 2-(2,4-dichlorophenoxy)-5-chlorophenol (triclosan) in chlorinated water samples was investigated. Sensitive determination of the parent compound and its transformation products was achieved by gas chromatography with mass spectrometry detection after sample concentration, using a solid-phase extraction sorbent and silylation of the target compounds. Experiments were accomplished using ultrapure water spiked with chlorine and triclosan concentrations in the low mg/l and ng/ml ranges respectively. Chlorination of the phenolic ring and cleavage of the ether bond were identified as the main triclosan degradation pathways. Both processes led to the production of two tetra- and a penta-chlorinated hydroxylated diphenyl ether, as well as 2,4-dichlorophenol. The formation of 2,3,4-trichlorophenol was not detected in any experiment; however, significant amounts of 2,4,6-trichlorophenol were noticed. All of these five compounds were also identified when triclosan was added to tap-water samples with free chlorine concentrations below 1 mg/l. Minor amounts of three di-hydroxylated phenols, containing from one to three atoms of chlorine in their structures, were also identified as unstable triclosan chlorination by-products. The analysis of several raw wastewater samples showed the co-existence of important concentrations of triclosan and its most stable by-products (2,4-dichlorophenol and 2,4,6-trichlorophenol), reinforcing the potential occurrence of the described transformations when products containing triclosan are mixed with chlorinated tap water.
KeywordsTriclosan Chlorination by-products Chlorophenols SPE GC-MS
This work has been financially supported by the Spanish DGICT (project BQU 2003-02090) and the Xunta de Galicia government (projects PGIDIT03TAM02E and PGIDIT04PXIC23701PN). P.C. acknowledges an FPU grant from the Spanish Ministry of Education. S.M. gratefully acknowledges financial support from Xunta de Galicia through a research scholarship.
- 6.Alaee M, D´Sa I, Bennett E, Letcher R (2003) Organohalogen Compd 62:136–138Google Scholar
- 13.Clesceri LS, Greenberg AE, Eaton AD (eds) (1998) Standard methods for the examination of water and wastewater, 20th edn. American Water Works Association, Maryland, pp 461–465Google Scholar
- 17.Patnaik P, Yang M, Powers E (2000) American Laboratory 32:16–17Google Scholar