Paper-based colorimetric sensor array for detection of trinitrotoluene using chemometric methods

The analysis of chemical contaminants in environmental matrices has attracted attention of many scientists in last decade. Trinitrotoluene (TNT) is one the significant, global environmental pollutant. Contamination of soil and groundwater with TNT is the major concern because of its biological persistence, toxicity and mutagenicity [1]. On-site analysis methods can be used to assess the nature and extent of contamination as well as to monitor remediation progress. Current on-site methods often involve multiple steps and are time consuming [2]. In this study we report a new visual colorimetric sensor array for detection of TNT.TNT has been identified based on its electron acceptance property. Accordingly, the color conversion of TNT in reaction with electron donors (ammines) has been considered according to the Meisenheimer complex reaction.In order to design a reproducible and cost efficient sensor array a set of 27 sensing elements were fabricated by using standard filter paper as a sensor substrate. The color conversion has been captured by a photographic camera. Here, based on color changes observable with the naked eye, the concentrations of up to 5 ppm are detectable. Then, nitrobenzene-based materials have been studied as interferences. Finally, captured images were converted to the analytical data by statistical analysis methods. Multivariate statistical methods like PCA and HCA were applied for analyzing the collected data. The use of colorimetric sensor array has proven to be a fast, inexpensive and versatile method for TNT analysis compared to the other techniques.