Development and testing of novel functionalized polymeric thin-films for equilibrium passive sampling of PFAS compounds in water

The demand for an accurate assessment of exposure and risk from the presence of per-and polyfluoroalkyl substances (PFAS) in the aquatic environment has created the need for new methods of measurements in water at sub-parts per trillion concentrations. We explored the concept of equilibrium passive sampling for PFAS using the strategy developed for other organic compounds. Equilibrium passive sampling should predict the concentration of the chemically labile fraction of PFAS in water based on equilibrium partitioning into the sampler, without the need for site-specific calibration. Our goals were to identify sampler materials with the potential to mimic PFAS partitioning into animals and sediments and provide reversible sorption in a time frame appropriate for in situ samplers. To achieve this goal, we tested a range of candidate materials, including three broad classes of polymers embedded with suitable sorbents for PFAS. The most promising synthesized thin films were activated carbon (AC) embedded in agarose, silica-bonded human serum albumin (s-HSA) embedded in Agarose, WAX embedded in cellulose acetate, and HLB embedded in PDMS, which yielded log sampler-water partition coefficients close to 3 for many PFAS compounds. Sampler equilibration time in water was approximately one week. Investigation of the isotherms suggested that the sorption can be described across the concentration range of interest, from the ng/L range commonly found in natural uncontaminated waters to the ug/L concentrations found in contaminated sites. Also, the selected films exhibited relatively rapid desorption of PFAS, indicating that the sorbents are capable of reversible, equilibrium measurements. The present study demonstrates a potential new approach to passive sampling of PFAS.