Redox-Based Electrochemical Affinity Sensor for Detection of Aqueous Pertechnetate Anion

Rapid, selective, and in situ detection of pertechnetate (TcO₄ ^-) in multicomponent matrices consisting of interfering anions such as the ubiquitous NO₃ ^- and Cl^- or the isostructural CrO₄ ^2- is challenging. Present sensors lack the selectivities to exclude these interferences or the sensitivities to meet detection limits that are lower than the drinking water standards across the globe. This work presents an affinity-based electrochemical sensor for TcO₄ ^- detection that relies on selective reductive precipitation of aqueous TcO₄ ^- induced by a 1,4-benzenedimethanethiol capture probe immobilized on an electrode platform. This results in a direct decrease in the electron transfer current, the magnitude of the decrease being proportional to the amount of TcO₄ ^- added. Using this approach, a detection limit of 1 × 10^-10 M was achieved, which is lower than the drinking water standard of 5.2 × 10^-10 M set by United States Environmental Protection Agency. The proposed approach shows selectivity to the TcO₄ ^- anion, allowing detection of TcO₄ ^- from a multicomponent groundwater sample obtained from a well at the Hanford site in Washington (well 299-W19-36) that also contained NO₃ ^-, Cl^-, and CrO₄ ^2-, without discernably affecting the detection limits.