Analytica Chimica Acta 575 (2006) 106–113 Formation of halogenated by-products of parabens in chlorinated water P. Canosa, I. Rodr´ ıguez ∗ , E. Rub´ ı, N. Negreira, R. Cela Departamento de Qu´ ımica Anal´ ıtica, Nutrici ´ on y Bromatolog´ ıa, Instituto de Investigaci´ on y An ´ alisis Alimentario, Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain Received 31 March 2006; received in revised form 19 May 2006; accepted 22 May 2006 Available online 27 May 2006 Abstract Chemical transformations of four alkyl esters of p-hydroxybenzoic acid, parabens, in chlorinated water samples are investigated. Quantification of the parent species and identification of their reaction by-products were performed using gas chromatography in combination with mass spectrometry. Experiments were accomplished considering free chlorine and paraben concentrations at the mg L -1 and gL -1 level, respectively. Concentration of water samples, using solid-phase extraction, and silylation of the target species were carried out in order to improve the detectability of parent species and their possible transformation products, achieving quantification limits at the low ng L -1 level. Under employed experimental conditions, the decrease in the concentrations of parabens followed pseudo-first-order kinetics. Half-lives values obtained for model ultrapure water solutions were in good agreement with those observed in tap water samples. For the first type of sample, only two by-products were detected for each paraben. They corresponded to chlorination of the aromatic ring in one or two carbons situated in ortho-positions to the hydroxyl group. Both species were also generated after the addition of parabens to chlorinated tap water. Moreover, three new transformation products were noticed for each parent compound. They were identified as bromo- and bromochloro-parabens, formed due to the existence of traces of bromide in tap water sources. Experiments carried out by mixing paraben-containing personal care products with tap water, containing free chlorine, confirmed the formation of all above described halogenated by-products. In addition, the presence of the di-chlorinated forms of methyl and propyl paraben has been detected for first time in raw sewage water samples. © 2006 Elsevier B.V. All rights reserved. Keywords: Parabens; Chlorine; Halogenated by-products; Water samples; Gas chromatography–mass spectrometry 1. Introduction Parabens, esters of p-hydroxybenzoic acid, are extensively employed as bactericides and preservative agents in antiperspi- rants, sunscreen creams, bath gels, shampoos and toothpaste [1]. As in the case of many personal care chemicals, they are continuously released in the aquatic media through domestic wastewater, therefore, a growing concern has arisen in relation to their potential long term effects on wildlife. Nowadays, it is known that parabens are weak endocrine disrupters [2] and, although they are removed in a considerable extension during conventional sewage water treatments [3], their presence has been detected in river water samples at the low ng L -1 level [4]. Moreover, recent studies have suggested a possible relation- ship between breast cancer and prolonged dermal expositions to paraben-containing products [5]. ∗ Corresponding author. Tel.: +34 981 563100x14387; fax: +34 981 595012. E-mail address: qnisaac@usc.es (I. Rodr´ ıguez). The possibility that personal care chemicals and non- prescription drugs might reach potable water sources has fos- tered different studies aiming to test their stability and to study the formation of undesirable by-products, during water chemical disinfection treatments [6]. This information is also relevant to improve their removal efficiency in sewage water plants using advanced oxidation processes. On the other hand, less atten- tion has been paid to the reactivity of personal care products when mixed with tap water in our homes. Independently of the primary disinfection treatment applied in production plants, tap water is normally amended with free chlorine to insure its bacteriological quality throughout the distribution system. Chlorine is a potent oxidant able to react with natural organic matter and anthropogenic chemicals rendering different halo- genated by-products. Some of them are toxic species, which might suppose a potential risk for human health [7,8]. Particu- larly, compounds containing phenolic groups in their structures show favourable chlorination kinetics [9–12]. As an example, recent studies have demonstrated that personal care products containing triclosan (5-chloro-2-(2,4-dichlorophenoxy) phenol) 0003-2670/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2006.05.068