Colorimetric Paper-Based Analytical Device for Perfluorooctanesulfonate Detection

Per- and polyfluoroalkyl substances (PFASs) are environmental contaminants of emerging concern due to being highly persistent, bioaccumulative, ubiquitous, and potentially toxic. Multiple instrument-based methods exist for sensitive and somewhat selective detection of PFASs but suffer from high costs, expensive laboratory equipment, and the need for highly trained personnel. Since PFASs can adversely impact human health, there is a need for fast, inexpensive, robust, and portable methods to detect PFASs outside the laboratory. This would enable identification of concentrated pollution sources as well as monitor contamination. Here, we present a paper-based analytical device (PAD) for detection of perfluorooctanesulfonate (PFOS), one of the most widespread PFASs. Based on a color change from the ion-pairing between PFOS and methylene green, PFOS can be quantified with the naked eye by measuring the diameter of the purple circle that is formed by the ion pair. A limit of detection (LOD) of 10 ppm was obtained. In this paper, we optimized the PAD and evaluated interferences from perfluorooctanoic acid (PFOA) and other surfactants commonly found in environmental samples as well as potential coexisting ions. With the help of a pretreatment and preconcentration step, this PAD can serve as a tool to identify areas of high PFOS contamination.