Detection of Brominated By-Products Using a Sensor Array Based on Nanostructured Thin Films of Conducting Polymers

The detection of the carcinogenic trihalomethanes (THM) in public water supplysystems using low-cost equipment has become an essential feature, since these compoundsmay be generated as by-products of water-treatment processes. Here we report on a sensorarray that extends the concept of an "electronic tongue" to detect small amounts ofbromoform, bromodichloromethane and dibromochloromethane, with detection limits aslow as 0.02 mg L^-1. The sensor array was made up of 10 sensing units, in whichnanostructured films of conducting and natural polymers were deposited onto goldinterdigitated electrodes. The principle of detection was impedance spectroscopy, withmeasurements carried out in the range between 1 Hz to 1 MHz. Using data at 1 kHz, atwhich the electrical response varied considerably by changing the analyte, we demonstratedwith principal component analysis (PCA) that samples with the 3 brominatedtrihalomethanes can be distinguished from each other and for various concentrations.