Methylene blue-mediated electrocatalytic detection of hexavalent chromium.

We report, for the first time, the design and fabrication of an electrochemical ion (E-ION) sensor for highly specific detection of hexavalent chromium (Cr(VI)). Unlike previously developed electrochemical Cr(VI) sensors, the sensing mechanism relies on the previously unexplored electrocatalytic reaction between Cr(VI) and surface-immobilized methylene blue (MB). The sensor is sensitive, specific, and selective enough to be used in a synthetic aquifer sample. Like many sensors of this class, it is also reagentless, reusable, and compatible with gold-plated screen-printed carbon electrodes. Despite the difference in the sensing mechanism, this E-ION Cr(VI) sensor possesses attributes similar to other MB-based electrochemical sensors, sensors with potential for real world applications.