Photometric determination of trivalent gallium, indium and thallium with Xylenol orange

Colorimetric Sensor Array for Qualitative Water Analysis

A chemosensor array comprising 45 off-the-shelf colorimetric dyes, dubbed the Singapore Tongue (SGT), that is capable of discriminating different brands of bottled water and waters of different geographical attribute is described. Twelve kinds of bottled waters were tested by the SGT, and changes of absorbance spectra were analyzed by unsupervised classification methods to validate the SGT system for water analysis. All 12 bottled waters were discriminated at 1 × concentration, and SGT could distinguish the identity of samples of the waters diluted up to 100 times, except distilled waters. Following the study of 63 tap waters in different mass rapid transit stations in Singapore, two distinct clusters were observed from a principal component analysis plot, which correspond to the origin of the tap water. The successful discrimination and identification of in this study demonstrates the practical application of the SGT as a simple tool for water analysis.