The presence of per- and polyfluoroalkyl substances (PFAS) in the news is almost as persistent as their presence in the environment; these so-called “forever chemicals” are complicated, durable and difficult to degrade, making them a threat to the environment and to human health.

In the UK, water companies have been told to tackle potentially high levels of these toxic chemicals in drinking water, with arguments to limit levels or ban them altogether. Meanwhile in the US, the first legally enforceable national drinking water limits for six PFAS, established under former President Joe Biden, are being rolled back.

PFAS in the environment can cause a number of problems, from contamination of soil and water to bioaccumulation, neurological and reproductive issues in wildlife. Current detection techniques are limited by our knowledge of PFAS whilst also being lengthy and laboratory-based; how are such limitations in the environmental analysis of PFAS being addressed, and can analysis be taken out of the lab and into the field?

“What makes PFAS useful is also what makes them very stable and difficult to degrade: they contain extremely strong carbon-fluorine (C-F) bonds, among the strongest in organic chemistry. These bonds give PFAS extremely high resistance to heat, water and biological degradation. Because they do not readily break down by conventional treatment technologies, they persist in the environment and accumulate in water, soil, air and the food chain,” explained Professor Silvana Andreescu, Egon Matijević Endowed Chair in chemistry and professor of bioanalytical chemistry at Clarkson University.

“Shorter-chain PFAS are more mobile in water and can spread through aquifers; longer-chain PFAS bioaccumulate more strongly, concentrating up the food chain. This combination of persistence, mobility and bioaccumulation means PFAS can be widespread even when released in a single point-source event,” added Professor Mujtaba Baqar of the Sustainable Development Study Centre at GC University Lahore and member of Professor Hongwen Sun and Professor Yiming Yao’s research group at Nankai University.

There is no “safe” space – PFAS are ubiquitous and travel over long distances. Although there are many sources of contamination, the most common include wastewater treatment plants, military and firefighting training areas, and consumer and industrial product discharges, where communities and wildlife are often exposed to higher levels of PFAS through ground, surface and drinking water.

The presence of these contaminants has been linked to numerous adverse health and environmental effects. Laboratory and epidemiological studies show they have a detrimental effect on organ systems, disrupt the endocrine system and may play a role in cancer.

“Ecologically, PFAS can impair reproduction and growth in wildlife, reduce resilience of aquatic organisms and change microbial community function in soils and sediments. The specific outcome depends on which PFAS, concentration, exposure route and the organism – but the precautionary conclusion is that widespread low-level contamination can cause long-term, population-level impacts,” said Baqar.

Current PFAS detection techniques

There are thousands of PFAS, meaning it’s challenging to study and assess the potential risks of each individual chemical. Some have been studied more than others, so what we know about them is based on the few, rather than the many.

Several analytical techniques may be used to detect PFAS, but the gold standard is liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS),“which is reliable and can distinguish PFAS compounds at very low levels,” said Andreescu.

This technique is typically used to quantify PFAS using multiple reaction monitoring (MRM) in water, serum or soil samples; Baqar says its strengths are “high sensitivity, robust quantitation and regulatory acceptance for many legacy PFAS (e.g., PFOA, PFOS),” but it “only measures chemicals for which standards and MRM transitions exist. Many PFAS precursors and novel replacement chemistries can’t be detected.”

It’s also expensive – up to $800 per sample – andtime consuming, and because samples must be sent to a central laboratory for analysis, it can’t be used in the field.

“Current technologies have low sample throughput, long wait times and are largely inaccessible to many labs and communities,” Andreescu continued. “There is a significant need for more practical cost-effective methods to measure PFAS more quickly and affordably. Until these methods are developed, LC-MS/MS remains the gold standard for PFAS measurements.” 

Other methods measure the overall fluorinated compounds content, or total fluorine. These include extractable organic fluorine (EOF), adsorbable organic fluorine (AOF) and the total oxidizable precursor (TOP) assay. These techniques estimate perfluoroalkyl acid precursors or the total organochlorine fraction but share several common practical limitations, including the limited availability of reference analytical standards, partial PFAS adsorption and entrapment of fluorinated inorganic anions on adsorbent materials.

Approaches like EOF/combustion ion chromatography (CIC) capture the total fraction of fluorine bound in organic molecules (organofluorine) in a sample after combustion. It’s “useful to show the presence of unidentified PFAS, but it’s non-specific – it gives the mass of fluorine but doesn’t provide a structure so can’t identify individual PFAS,” explained Baqar. AOF – which is also often combined with CIC – focuses on aqueous samples and captures ionic, neutral and zwitterionic organofluorines on an adsorbent but struggles with ultrashort-chain PFAS. ​

TOP assays target PFAS predecessors; “chemical oxidation converts many PFAS precursors into stable perfluoroalkyl acids (PFAAs) like PFOA/PFNA which are then quantified by LC–MS/MS. The difference before/after oxidation estimates precursor burden,” said Baqar. “This technique is useful for revealing hidden precursor pools that targeted methods may miss, but not all precursors are oxidized equally and as it’s an operationally defined assay (not chemical identification), it does not identify original structures.”

Professor Sun’s research groupcombines TOP, EOF and high-resolution mass spectrometry (HRMS) to identify known and previously unrecognized fluorinated compounds and assess their contribution to total PFAS burdens. This provides a comprehensive framework for PFAS environmental monitoring and addresses gaps in PFAS detection and characterization.

“HRMS provides accurate mass and high resolving power,” explained Baqar. “You can run targeted lists, suspect screening (searching exact masses for known formulas without standards), or full non-target analysis to discover unknown fluorinated compounds; MS/MS fragmentation patterns help structural annotation.”

The technique can reveal novel PFAS and precursors, assign empirical formulas and perform retrospective data mining. “It’s excellent for expanding the known universe of PFAS,”, but, according to Baqar, “identification confidence without standards can be low and quantitation is semi-quantitative unless authentic standards become available, and data analysis is computationally demanding.”

The need for better PFAS testing

Increased regulation of PFAS requires improved testing, and Andreescu says there is “considerable activity in industry and academia to improve existing methods and create new detection methodologies and devices to enhance portability, reduce cost and expand accessibility for large-scale use, and reduce reliance on centralized labs.”

This includes optical-based methods that measure color, fluorescence or refractive index, and electrochemistry which measures electrical changes that occur when PFAS binds to conductive electrode surfaces.

Nanosensors are also a promising area of research, and in 2024, Andreescu received nearly $1.5 million from the US Environmental Protection Agency to develop integrated nanosensor technology for field detection and degradation of PFAS in groundwater or surface water that may be used as drinking water sources.

“Nanosensors are designed to provide rapid detection by converting molecular binding events into measurable signals. They take advantage of the large surfaces area, enhanced reactivity and distinctive optical, sorptive and electronic properties of nanomaterials, which make them particularly effective for PFAS binding,” explained Andreescu.

When integrated with optical or electrochemical platforms, nanosensing platforms provide superior sensitivity, selectivity and efficiency, enabling detection at very low concentration levels. “For example, nanomaterials amplify surface enhanced Raman signals, which allows more sensitive detection of PFAS molecules adsorbed on their surface,” Andreescu said.

“Optical nanosensors typically use fluorescent molecular receptors that change optical signatures when PFAS bind to them. Electrochemical sensors that measure PFAS binding to electrode surfaces modified with redox receptors, redox polymers or nanomaterials, detect PFAS at parts-per-trillion (ppt) levels.”

Such technology could be used to provide immediate feedback on PFAS concentrations in the field, making them ideal for low-cost portable detection, and use as screening devices for assessment of contamination and remediation efforts.They could alsooffer greater spatial and temporal data reasoning, and more comprehensive characterization and screening.

“The advantage of these methods is that they can use widely available instrumentation, are relatively inexpensive and can be developed as portable field deployable devices,” explained Andreescu. “However, PFAS lack functional groups that are measurable by these techniques, and therefore there is a need to innovate new types of probes, chemical approaches and detection strategies that can bind and selectively recognize PFAS.”

Most current research is focused on this area, but other active areas include the development of molecular receptors that can recognize and bind specific PFAS as well as the application of machine-learning to distinguish and classify PFAS compounds. These strategies can improve selectivity and detection accuracy, and when available, these methods can provide faster results and be used to rapidly estimate PFAS concentrations at low cost, Andreescu says. They may also be used in remediation operations, for example to compare PFAS concentrations before and after treatment, to evaluate PFAS reduction and the effectiveness of remediation efforts.

Andreescu believes there is considerable effort and promise in these technologies, with several studies demonstrating “very encouraging detection performance.” Current efforts to advance these sensors to the field focus on improving manufacturing, developing approaches for more reliable detection, and to validate their performance against the gold standard method for PFAS detection.

“These sensors can be used in many ways,” Andreescu said. “A particularly promising application is the integration of PFAS sensors with remediation technologies to monitor the effectiveness of remediation efforts in real time. Other applications are for at-home testing of drinking water wells or as screening tools for large-scale monitoring of PFAS contamination. While these sensors may not be as precise as LC-MS/MS, they could offer a fast, affordable way to track PFAS more broadly at low cost, thus enabling more widespread monitoring of contamination.”

And that’s the key; PFAS are ubiquitous and numerous, yet our knowledge is based on just a handful. As we learn more about these forever chemicals, it’s clear that monitoring needs to be more widespread, but improvements in detection methods must also be made. Much research is focusing on streamlining the process, taking detection methods out of the lab and into the field.