Sensitive determination and discrimination of fluorinated ions using ion-transfer voltammetry.

We propose a sensitive method for discriminating fluorinated from non-fluorinated ions using ion-transfer voltammetry. This approach employed supported liquid membranes (SLMs) impregnated with either a fluorous solvent, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OFE), or an organic solvent, 1,6-dichlorohexane (DCH). Ion-transfer reactions of the fluorinated ion perfluorooctanoate (PFOA−) and various non-fluorinated anions were measured at both the SLM(OFE)|water (W) and SLM(DCH)|W interfaces. Fluorinated ions exhibit fluorophilicity, while non-fluorinated ions show fluorophobicity toward fluorous solvents. Consequently, the shifts in the recorded ion-transfer potentials for PFOA− and non-fluorinated ions between the SLM(OFE)|W and SLM(DCH)|W interfaces exhibited opposite trends, indicating that fluorinated ions can be readily discriminated through voltammetric measurements. Furthermore, electrochemical preconcentration of PFOA− into the SLM proved feasible, enabling sensitive determination of PFOA− by subsequent voltammetric measurement. The proposed method is simple and cost-effective, making it a promising approach for the analysis of problematic per- and polyfluoroalkyl substances.