Sensors and Actuators B 208 (2015) 622–627 Contents lists available at ScienceDirect Sensors and Actuators B: Chemical jo u r nal homep age: www.elsevier.com/locate/snb Innovative colorimetric sensors for the selective detection of monochloramine in air and in water T.-H. Nguyen a,b , L. Mugherli a,c,∗ , C. Rivron a,c , T.-H. Tran-Thi a,c a CEA, DSM, IRAMIS, NIMBE, LEDNA, URA CEA-CNRS 2453, 91191 Gif-sur-Yvette Cedex, France b ETHERA R&D, CEA, Saclay, Bât. 451, F-91191 Gif-sur-Yvette Cedex, France c CNRS, DSM, IRAMIS, NIMBE, LEDNA, URA CEA-CNRS 2453, 91191 Gif-sur-Yvette Cedex, France a r t i c l e i n f o Article history: Available online 1 November 2014 Keywords: Colorimetric sensors Monochloramine Nanoporous matrices Pollutant Swimming pool a b s t r a c t The development of a new disposable chemical sensor for the direct and selective detection of monochlo- ramine, NH 2 Cl, a toxic pollutant present in both water and atmosphere of indoor swimming pools, is described. This innovative chemical and colorimetric sensor is based on the use of nanoporous matrices doped with probe-molecules, which act as sponges to trap the targeted pollutant and turn from trans- parent to dark blue. The calibration for gaseous NH 2 Cl was carried out with concentrations ranging from 60 to 250 ppb at room temperature and in humid atmosphere. In water the detection limit of NH 2 Cl is 0.01 mg/L. This method, which is selective and easy-to-use, could favorably replace the current method of detection of free and combined chlorine used in swimming pools. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The detection and analysis of toxic halogenated compounds at ppb level is of great importance because of the health damages related to their inhalation or ingestion, even at low concentra- tion. In swimming-pools, chlorine (Cl 2 ) is used as a disinfectant to minimize the risk to users from microbial contaminants. In water, Cl 2 is transformed into hypochlorous acid (HClO) which reacts with nitrogen compounds generated by human secretions such as saliva, sweat, or urine, leading to the formation of sev- eral chloramines, such as monochloramine (NH 2 Cl), dichloramine (NHCl 2 ) and nitrogen trichloride (NCl 3 ) [1]. NCl 3 , the most volatile and toxic chloramine, provokes significant eye and respiratory irri- tations in swimmers and pool-attendants [2]. NH 2 Cl is known to remain active in water for a considerably long period of time and does not produce by-products such as trihalomethanes. For these reasons, it is often used with typical concentrations of 0.5–2 mg/L to decontaminate drinking water. Although NH 2 Cl has been shown to be mutagenic in some in vitro studies, it has not been found to be genotoxic in vivo [3]. In the absence of data on human cancer and on the basis of inadequate evidence for the carcinogenicity of monochloramine in experimental animals, monochloramine was ∗ Corresponding author. Tel.: +33 0169089427. E-mail address: laurent.mugherli@cea.fr (L. Mugherli). evaluated by the International Agency for Research on Cancer, IARC, as not classifiable as to its carcinogenicity (Group 3). The guideline value of NH 2 Cl in drinking water proposed by the World Health Organization is 3 mg/L [3]. Recently we have shown that it is possible to detect ppb amount of gaseous NCl 3 in the atmosphere of indoor swimming pools with nanoporous matrices doped with NaI/Amylose [4]. These nanoporous sensors are now produced by ETHERA and commer- cialized by CIFEC. The next swimming-pool pollutant targeted was NH 2 Cl. As NH 2 Cl is less volatile than NCl 3 , the work presented in this paper aimed at producing nanoporous sensors for the selective detection of NH 2 Cl in water and in air. Some apparatus for the detection of NH 2 Cl exist and are already on the market. The Model CL from Emerson, a mem- brane covered amperometric sensor can detect NH 2 Cl at ppm level (0–15 ppm), but free chlorine and other oxidizing agents may affect the response of sensors [5]. Currently, the method to selectively detect NH 2 Cl is based on the Berthelot reaction [6]. Among the three chloramines, only NH 2 Cl has two exchangeable protons which can react with phenol to produce indophenol, a col- ored compound which absorbs at 635 nm. This method is widely applied to the manufacturing of online ammonia (NH 3 ) analyzers. Ammonia is first converted to monochloramine by the addition of hypochlorous acid (HOCl) in alkaline solution, and then phenol is added in excess to react totally with NH 2 Cl, producing indophenol (Fig. 1). http://dx.doi.org/10.1016/j.snb.2014.10.108 0925-4005/© 2014 Elsevier B.V. All rights reserved.