Towards selective detection of “forever chemicals”: development of opto-electrochemical sensor array for perfluorooctanoicacid (PFOA)

The methodology of opto-electrochemical detection of "forever chemical" perfluorooctanoic acid (PFOA) at ppt level is developed. The approach consists in cathodic pre-concentration of PFOA on the surface of biochar- modified screen-printed electrodes (BC-SPE) followed by its defragmentation into partially hydrogenated PFOA chains and release of proportional amount of F- ions. The F- concentration was estimated with on- paper-based optical sensor array based on silicon and aluminum corrolates, SiTTC and AlTPF5C respectively. The data of BC-SPE electroreduction currents, fluorescence and luminescence intensity of SiTTC and AlTPF5C -based optodes fused together were used to construct PLS1 calibration model that has permitted PFOA quantification in concentration range from 40 ng/l to 4 mg/l with the lowest detection limit of 15 ppt and R-2 of 0.896.