Comparison of 2-mercaptoethane sulfonate and mercaptoacetic acid disorganized monolayer-coated electrodes for the detection of copper via underpotential deposition-stripping voltammetry

The presence of electrode-passivating compounds in many natural samples constitutes a challenge for analytical detection therein using electrochemical techniques. This work reports the spontaneous adsorption of short-chain thiols onto a gold surface to form a thin and porous film which protects the electrode surface from the adsorption of surfactants while simultaneously allowing the underpotential deposition and stripping of metals. A direct comparison of two disorganized monolayer films (2-mercaptoethane sulfonate, MES, and mercaptoacetic acid, MAA) for the detection of copper by voltammetric stripping of underpotential deposits and for the protection of the electrode surface from surfactants is presented. These modified electrodes present similar behaviors, both fulfilling the disorganized monolayer approach requirements of surfactant exclusion while maintaining analyte accessibility to the underlying electrode.