Detection of diverse potential threats in water with an array of optical sensors

•Combinatorial preparation of sensing materials blending porphyrins, pH indicators and exchanger salts.•Multivariate identification, independent from concentration, of a series of noxious compounds of different chemical structure.•Characterization of the optical sensors in terms of response curve and sensitivity. Optical sensor arrays are widely used for sensing the evolution and the identification of complex patterns of chemicals either in air or in water. This popularity stems from the fact that low-cost, ready-to-use optical devices, made available by the current commercial development of electronics commodities, are complemented by a number of low-cost chemical indicators, suitable for a wide range of applications. Among them, pH indicators, and metalloporphyrins make a solid library of molecules that can be adequately assembled for many different tasks. Here, such an array is used for the identification of toxic compounds of different origin that may be released in water distribution systems as a consequence of either accidents or deliberated contaminations. The compounds considered are intermediate products of chemical industry (dimethyl methylphosphonate and cyclohexanone), drugs (5-Fluorouracil and piperazine) and pesticides (imidacloprid and paraoxon). Results show that the sensors are sensitive, but with low selectivity, in the interval from 10−7molL−1 to 10−4molL−1. The sensor signals show a linear correlation with the logarithm of the concentration. Although the limited selectivity of individual sensors, the different sensitivity patterns allow for a clear identification of the compounds, independent of their concentration.