Electrode Selection for an Electrochemical Sensor for Perfluorooctanoic Acid using Molecularly Imprinted Polymers

Abstract

An electrochemical PFAS-sensor for perfluorooctanoic acid (PFOA) using moleculary imprinted polymer (MIP) is made. Electropolymerization is used for the synthesis of a MIP layer for PFOA on top of an electrode. The MIP layer is a polymer layer to which PFOA has a high binding affinity. A redox probe is added to monitor the electrochemical signal. When PFOA is present, it enters the cavities of the MIP layer. This prevents the redox probe from reaching the electrodes surface, which causes a decrease in the electrochemical signal for increasing PFOA concentrations. Cyclic voltammetry, differential pulse voltammetry and square wave voltammetry were used to measure the electrochemical signal.

An electrode selection is done to find the electrode most suitable for the preparation of an electrochemical PFAS-sensor for PFOA. Carbon and gold screen printed electrodes, gold and platinum microelectrodes, a glassy carbon electrode and an interdigitated electrode are used. The glassy carbon electrode is likely the most suitable electrode for the preparation of an electrochemical PFAS-sensor for PFOA, because it has a smooth electrode surface, a stable MIP layer and a stable electrochemical signal. However, non of the electrodes gave a decrease in the electrochemical signal for increasing PFOA concentrations. Instead, PFOA was found to cause an increase in the electrochemical signal, which is attributed to the adsorption of PFOA on the electrode. This could influence the oxidation of the redox probe causing an increase in peak current.

Furthermore, the thickness of the MIP layer was measured using a Dektak profilometer and an atomic force microscope. It was found that the thickness of a MIP layer can be controlled by varying the parameters of the electropolymerization.