Journal of Chromatography A, 1310 (2013) 98–112 Contents lists available at ScienceDirect Journal of Chromatography A j our nal homep age: www.elsevier.com/locate/chroma Using mass spectrometry to highlight structures of degradation compounds obtained by photolysis of chloroacetamides: Case of acetochlor Yasmine Souissi a , Sophie Bourcier a,∗ , Sélim Ait-Aissa b , Emmanuelle Maillot-Maréchal b , Stéphane Bouchonnet a , Christophe Genty a , Michel Sablier a a Ecole Polytechnique, Laboratoire des Mécanismes Réactionnels, CNRS, Route de Saclay, 91128 Palaiseau Cedex, France b INERIS, Unité Ecotoxicologie in vitro et in vivo, Parc ALATA, BP2, 60550 Verneuil en Halatte, France a r t i c l e i n f o Article history: Received 30 January 2013 Received in revised form 22 July 2013 Accepted 23 July 2013 Available online 31 July 2013 Keywords: Acetochlor Mass spectrometry Identification of photoproducts In vitro assay Potential toxicity a b s t r a c t The photooxidation of acetochlor (a pesticide belonging to the acetamides group) using a polychromatic UV irradiation in ultrapure water was studied. This study reports the efficiency of mass spectrometry for the characterization of photodegradation products of acetochlor. Decompositions of protonated ions MH + are proposed in electrospray (ESI) mode for LC–MS, while electron ionization (EI) and chemical ionization modes (CI) are used for GC–MS. The knowledge of fragmentation and the use of a combination of experiments (MS/MS, high resolution) allow the characterization of photoproducts. Structural eluci- dation is assisted by the use of photolysed deuterated compounds. Fifteen major degradation products have been characterized, five by LC-QTOF, six photoproducts by GC-ITMS, and four are observed by both techniques. In vitro bioassays based on the quantification of receptor-mediated activity demonstrated that acetochlor photolysis engenders a moderate but significant estrogenic activity. Moreover, a quanti- tative structure–activity relationship (QSAR) approach was used to assess the potential toxicity effect of acetochlor and its by-products. The predictions were analyzed showing a variety of toxicity profiles of acetochlor photoproducts depending on the toxicological investigated endpoint. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Due to their extensive use worldwide, an increasing num- ber of biologically active compounds belonging to a large variety of chemicals appear in different aquatic environments under the form of the parent molecules and their degradation prod- ucts. The contamination of soils, ground and/or surface water is a growing environmental concern all over the world [1]. As a consequence, a large group of organic compounds have been labeled as water emerging contaminants by the Environmental Protection Agency [2] and the European Union [3]. The resulting directives which prioritize some of these compounds due to their high toxicity, high environmental persistence, and bioaccumula- tion potential include pesticides, among which are the chlorinated herbicides. These are of particular environmental concern due to their solubility and bioavailability. This represents a threaten- ing issue for aquatic environment and human health. Herbicides ∗ Corresponding author at: Ecole Polytechnique, Laboratoire des Mécanismes Réactionnels, CNRS, Route de Saclay, 91128 Palaiseau Cedex, France. Tel.: +33 1 69 33 48 06. E-mail address: sophie.bourcier@dcmr.polytechnique.fr (S. Bourcier). contaminated lands and farming areas may then require remedia- tion to reduce water resources contamination. In the present study, we focused on acetochlor [2-chloro-N-(ethoxymethyl)-N-(2-ethyl- 6-methylphenyl)acetamide], a member of the chloroacetanilide class of broad leaf herbicides, which is currently authorized and widely used as a pre- and post-emergence treatment. It is mainly absorbed by the roots and leaves, inhibiting photosynthetic elec- tron transport of the host [4]. The chloroacetanilide herbicides are frequently detected in water bodies located nearby agriculture areas after soil leaching and urban runoff [5,6]. While need to be monitored, their per- sistence in soil as well as the emergence of potential breakdown products is a non desirable effect that may lead to ecological and human health alterations [7,8] In fact, chloroacetanilide degra- dation products were reported to be detected with even greater frequency than the parent compound [9]. Recently, chloroacetanilide herbicides and their degradation products have been demonstrated to be potential endocrine disruptors. Acetochlor was also previously reported to have inter- actions with uterine estrogen receptors and to cause the alteration of thyroid hormone dependent gene expression [10,11]. Other studies pointed out that neutral chloroacetanilide herbi- cide degradates require closer attention as they became considered 0021-9673/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.chroma.2013.07.091