Solid state dual electrode electroanalysis under hydrodynamic conditions: Application to pH-controlled in-line sensing.

While electrochemically driven, pH control-enabled, dual electrode sensing under quiescent conditions is emerging as a viable electroanalytical method, application of this approach under hydrodynamic conditions is less well documented. In this work we report the development of a finite element model (COMSOL Multiphysics™) to simulate electrochemical pH control under both quiescent and hydrodynamic conditions. We used these simulations to elucidate the effect of flowrate on our pH control method. Adjustments to the applied currents were made so as to compensate for the removal of generated protons by hydrodynamic flow, thereby allowing effective pH control under different flow conditions. Once optimised, this approach was applied to the detection of hypochlorous acid under various flow rates. To this end, the sensitivity of the sensors benefitted from both the localized electrochemical pH control and the signal-boosting effect associated with hydrodynamic forces.