Cheap and Simple Electrochemical Sensors with Closed-Cell MIP-Coated Bipolar Electrode Arrays for Sub-Ppb Detection of PFOS in Water

Abstract

Growing public awareness of the health risks associated with long-term exposure to poly- and perfluoroalkyl substances (PFAS) has necessitated the development of low-cost, point of use, and accessible methods for detection in water. Efforts to develop such methods have been stymied by their very low concentrations (part per trillion level) and remarkable chemical stability. Recently, our group has developed a new technique termed optical anodic stripping voltammetry (o-ASV) which couples a closed-cell continuous bipolar electrochemical (BPE) sensor with cathodic electrochemiluminescence (ECL) reporting for the simple, rapid, and point-of-use detection of heavy metal ions in water. The work presented here, on the other hand, is aimed at adapting this same sensor transduction scheme to the quantitation of PFAS compounds. The primary challenge is accommodating the electrochemical inactivity exhibited by most PFAS compounds. This presentation will describe development of a molecular imprint polymer (MIP) layer on the surface of the sensor BPE to promote both selectivity and sensitivity in detection. The MIP layer works in combination with a proxy redox probe, ferrocene carboxylate (FcCOOH), to transduce the current signal to an optical readout that can be read with a digital camera like those on most modern cellular phones. This presentation will focus on describing the nature of the sensor transduction principle as applied to non-redox active PFAS compounds like perfluorooctanoic sulfonate (PFOS). A specific discussion of the operative mechanistic components of detection will be addressed, including the interplay between molecular adsorption, diffusion, and electrochemical transformation. Details of the stability and functional longevity of the electropolymerized MIP layer will be discussed along with its application to other isomorphic PFAS compounds. Finally, a new simple device fabrication procedure will be highlighted as it pertains to the open-source production of these novel sensors.