Co(II) triggered radical reaction between SO2 and o-phenylenediamine for highly selective visual colorimetric detection of SO2 gas and its derivatives

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Department of Materials Science and Engineering


Rapid, reliable, and highly selective detection of SO2 and its derivatives has an especially important practical significance in terms of environmental monitoring and human health. In this study, we describe a novel Co2+ triggered radical reaction pathway for visual colorimetric detection of SO2 and SO32−. The reaction between Co2+ and SO2 or SO32− with the assistance of dissolved oxygen produces highly active sulfate radical, leading to the oxidation of o-phenylenediamine (OPD). The oxidation products containing 2,3-dinitro-phenazinemethane, OPD dimer, and OPD trimer show strong UV–vis absorption. Consequently, SO2 and SO32− are quantitatively determined using the Co2+-OPD colorimetric detection system. This colorimetric assay exhibits a 60–650 μM and 30–70 ppm linear ranges for detection of SO32− and SO2, respectively. The corresponding limit of detection is calculated to be 4.07 μM and 1.26 ppm for SO32− and SO2. What is more, a distinct color change can be found at a SO32− concentration of 50 μM by the naked-eye observation. The specific radical detection guarantees that the present colorimetric assay has a good anti-interference ability over common inorganic ions and gases.

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© 2019 Elsevier B.V. Publisher's version of record:

Publication Title

Sensors and Actuators B: Chemical