Semi-quantitative colorimetric and supersensitive electrochemical sensors for mercury using rhodamine b hydrazide thio derivative

Mercury is a toxic heavy metal which pollutes air, land, and water posing a serious threat to the environment and human health. For a first-hand estimate, a qualitative method (colorimetric) for detection of mercury could suffice. However for precise measurement, below the threshold value, a quantitative method (electrochemical) is needed. The colorimetric strips were produced using mercapto-propionic add derivatized rhodamine hydrazide (RS). RS developed a pink color when in contact with mercury (Hg2+) and the shade became darker with an increase in concentration. A new polymeric hydrogel was used to entrap RS to fabricate sensing strips for quasi-quantitative detection of Hg2+ through the naked eye. An electrochemical sensor was also developed for accurate quantification of Hg2+ at ppt level by modified glassy carbon electrode with the same RS and green reduced graphene oxide (RS-gRGO/GCE) via differential pulse anodic stripping voltammetry (DPASV).The dipstick exhibited high sensitivity, good selectivity and low detection limit (0.29 ppb) whereas metal free, label-free modified electrode performed very well with a high sensitivity (70.22 mu A.ppb.cm(-2)), low detection limit (57 ppt), good selectivity, and reproducibility. These sensors will serve the purpose of common people for onsite estimation as well as scientific laboratories requiring precision measurements. (C) 2018 Published by Elsevier B.V.