Identification and determination of multiple heavy metal ions using a miniaturized paper-based optical device

A simple colorimetric paper-based sensor array (optical tongue), which can quickly and accurately identify and discriminate twenty-five kinds of heavy metal ions, is developed. It functions by immobilizing six metal indicators on the paper substrate using polyvinyl chloride. Exposing the device to the aqueous solution of metal ions produces a unique colorimetric signature for each ion, enabling discrimination of the ions by visual inspection. Further analysis of the colorimetric patterns by chemometrics data analysis methods leads to a clustering map for accurate classifying of the metal ions at different concentrations (10.0, 5.0, 2.5, and 1.0 mg L -1 ). In addition, the device was applied to analyze binary and ternary mixtures of metal ions as well. An interesting feature of this tasting device is speciation analysis of an element of different oxidation states and their mixtures. Beside to qualitative analysis, it represented quantitative analysis ability, e.g., for Zn 2+ and Co 2+ , in the concentration ranges of 0.10 to 10.00 mg L −1 (R 2 = 0.99) and 0.25 to 12.50 mg L −1 (R 2 = 0.99) and detection limits of 0.03 and 0.08 mg L -1 , respectively. This optoelectronic tongue shows promising results to be used potentially of on-site analysis of water for its quality. • An optical tongue, which can quickly identify and discriminate 25 heavy metal ions. • Immobilizing of the indicators on the paper surface hinders licking of the indicators. • The device can analyze sample solution, without need to any pretreatment. • The device produces a unique colorimetric signature for each ion. • Has potentially in on-site analysis of water for its quality.