A new, simpler method for detecting PFAS in water

Researchers have discovered a new way to detect per- and polyfluoroalkyl substances (PFAS) in water, marking an important step forward in creating testing devices that are simpler, more cost-effective, faster and generally more accessible than existing methods. Their method has been published in the journal Science Advances.

PFAS, so-called forever chemicals, have been recognised as a concerning pollutant. These chemicals persist in the environment because they resist breaking down and pose significant health threats. Exposure to these chemicals is linked to various cancers (including kidney, testicular, breast, ovarian, prostate, thyroid and childhood leukaemia), liver and heart damage, and developmental damage to infants and children.

Earlier this year, the US Environmental Protection Agency (EPA) announced the first ever national safety standard for PFAS in drinking water at 4 ppt. That means in a trillion molecules in water, only four molecules are allowed to be PFAS — and scientists need to be able to detect those few molecules.

The gold standard for testing PFAS is currently liquid chromatography combined with mass spectrometry. However, this method requires million-dollar equipment and complicated extraction steps, and is also not portable.

“In addition, the stubborn persistence of PFAS residues can diminish the sensitivity of these instruments over time,” said Xiaojun Wei, first author of the paper and currently a research assistant professor at the University of Massachusetts Amherst.

The new method works by adding a molecule called cyclodextrin to a small device that is typically used for sequencing DNA, called a nanopore. The ‘host–guest’ interaction between cyclodextrin and PFAS has been well documented, but according to corresponding author Chang Liu, no one had ever combined it with a nanopore for detection.

“Now we’re using one of these molecules, called HP-gamma-Cyclodextrin, as an adapter in an alpha-Hemolysin nanopore,” said Liu, who is currently an associate professor at UMass Amherst. This resulted in the creation of a PFAS detector.

The researchers demonstrated that their small, inexpensive device is feasible for identifying various PFAS families and detecting PFAS at levels as low as 400 ppt. And while their proof of concept does not reach the same level of sensitivity or the breadth of PFAS types that can be detected compared to mass spectrometry, the researchers see high potential for its impact — including as a first-screening tool to identify the water that poses the greatest risks to human health.

“We’re bringing the cost of the instrument from the scale of a million dollars to a few thousand,” said Liu, who hopes the team’s research will eventually lead to a commercialised portable PFAS detector for water monitoring in the field. “We need better technology for detecting PFAS — more accessible, more affordable and easier to use. And more testing that’s onsite. That’s the motivation.”

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