Fluorescence-Solid Phase Extraction (F-SPE) Platform for Rapid, On-site Detection of PFAS

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Project Summary Per-and polyfluoroalkyl substances (PFAS) have become an emerging class of water pollutants that cause serious environmental and health concerns. Due to their wide use in industry, military, and fire protection, PFAS have been spread and present in all kinds of water bodies. Among the over thousand PFAS ever manufactured and used, perfluorooctanesulfonic (PFOS) and perfluorooctanoic acid (PFOA) represent the top two PFAS used and studied the most for health effects. Recent studies indicate a tight linkage between exposure to these PFAS and many kinds of diseases and health effects. Currently, the advisory level set by the US EPA set for PFOS and PFOA in drinking water is 70 ppt (0.14 and 0.17 nM for PFOS and PFOA). Current detection of PFAS is mostly based on liquid chromatography coupled with mass spectrometry (LC-MS). However, the costs, footprint, power requirements, and sample preparation processes often associated with the LC-MS technologies limit their deployment beyond the formal laboratory setting. Especially for the detection of nanomolar levels of PFAS, LC-MS usually requires a preconcentration frontend device, making the analysis even more time-consuming. It becomes imperative to develop a rapid, simple, and low-cost sensor technology that is more suited for quick onsite detection of PFAS. While many chemical sensors, such as those based on fluorescence modulation, have been developed for the detection of PFAS, most of them are still far from sufficient for potable water analysis regarding either sensitivity (vs. 70 ppt) or selectivity (against the common chemicals, especially detergents). This project aims to fill this technical gap by developing a unique sensor platform that is small and easy to use, offering sensitive and selective infield detection of PFOS and PFOA (selected as the representative PFAS analytes). The sensor platform is based on highly sensitive and selective fluorescence sensors coated onto solid-phase extraction (SPE) capable of preconcentration of low concentrations of analyses, thus lowering the detection limit. The combination of preconcentration of SPE and fluorescence detection in one platform (namely F-SPE) would significantly simplify and speed up the analysis process. Moreover, F-SPE takes the principle of negligible depletion (ND) intrinsic to SPE, which would further simplify the analysis process by eliminating the need to precisely meter the sample volume as typically required for conventional analytical methods. ND relies on passing the minimal amount of sample through the membrane that is required for the analyte extraction to reach equilibrium. At this point, the analyte concentrations in the sample entering and exiting the membrane are equal. As a result, the surface concentration of the analyte can be directly correlated to its concentration in the sample but is no longer dependent on the volume of the sample passed through the membrane. Therefore, it is no longer necessary to meter an exact sample volume through the membrane. The main innovation herein lies in integrating the high sensitivity and selectivity of fluorescence sensors with the preconcentration capability and ND principle of SPE, which will enable quick, reliable detection of PFAS in a simple, low-cost way. The project will be implemented around three specific aims: Specific Aim 1. Synthesis and surface immobilization of fluorophores selective to either PFOS or PFOA to in-house fabricated SPE disks. Specific Aim 2. Evaluation of F-SPE/ND for PFOS and PFOA detection. Specific Aim 3. Commercialization Assessment.