Aquatic degradation of triclosan and formation of toxic chlorophenols in presence of low concentrations of free chlorine |
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Authors: | P Canosa S Morales I Rodríguez E Rubí R Cela M Gómez |
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Institution: | (1) Departamento de Química Analítica, Nutrición y Bromatología; Instituto de Investigación y Análisis Alimentario, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain;(2) Centro de Bioactivos Químicos, Universidad Central de Las Villas, 54830 Santa Clara, Cuba;(3) Labaqua S.A., 15702 Santiago de Compostela, Spain |
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Abstract: | 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. |
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Keywords: | Triclosan Chlorination by-products Chlorophenols SPE GC-MS |
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