Measuring PFAS concentrations in surface waters can be technically challenging due to their low concentrations in the parts-per-trillion range. Passive sampling approaches are attractive because they use pre-concentration by field deployed miniature devices to reach PFAS levels detectable by laboratory analytical methods.
SRP researchers from the University of Rhode Island and Brown University have recently announced a new type of PFAS passive sampler based on porous graphene hydrogel monoliths (see Figure). These miniature cylinders collect PFAS from aquatic environments by adsorption on the ultra-high internal surface area of self-assembled graphene nanosheets, which can then be extracted and quantified by mass spectrometry.
A key finding from the team is that the internal graphene surfaces can be modified by chemical grafting to impart positive electrical charge that greatly increases their affinity for anionic short-chain PFAS, which overcomes a limitation seen in existing sorbents and passive samplers. The work was led by the Jitka Becanova in the Rainer Lohmann laboratory at URI (passive sampling and analytical chemistry) and Zachary Saleeba in the Robert Hurt laboratory at Brown (device fabrication and chemical surface grafting). Their recently accepted publication describes the graphene hydrogel monolith synthesis, its surface modification, laboratory measurements of PFAS partition coefficients, and field demonstrations in the Delaware River. It is available on-line through the website of the Royal Chemical Society journal: Environmental Science Nano here.