Innovative Approaches for PFAS Detection
Credit: iStock
Growing evidence indicates that exposure to per- and polyfluoroalkyl substances (PFAS) can have serious health implications.
However, traditional analytical methods for PFAS analysis often require complex procedures and expensive equipment, making widespread testing difficult. As a result, there is an urgent need for innovative detection techniques that are both efficient and accessible.
This article provides an in-depth exploration of innovative detection techniques and the challenges faced in accurately quantifying PFAS in various samples.
Download this article to discover:
- Emerging technologies designed to address environmental contamination
- Detailed insights into novel detection methods and their applications in real-world scenarios
- Strategies for overcoming the complexities of PFAS analysis to safeguard public health
1
Article
Identifying and Characterizing
PFAS Compounds
Alexander Beadle
Per- and polyfluoroalkyl substances (PFAS) are a large family of synthetic chemicals, first discovered in
the 1940s. On account of their superior ability to resist heat, oil and stains, PFAS quickly became incorporated into everyday products such as cosmetics, firefighting foams, cookware and other household
materials.1
In the following decades, scientists would begin to raise concerns over the environmental impact of PFAS,
as these compounds do not readily break down in nature and so can become a persistent pollutant. In
response, some jurisdictions would introduce regulations aimed at discouraging the use of PFAS, in addition to implementing testing regimens to help mitigate the risk of PFAS pollution in drinking water, food,
agriculture and wildlife environments.2
Scientifically speaking, the detection and characterization of PFAS is no easy task. The sheer volume of
different compounds that exist under the PFAS umbrella can make it difficult for analytical scientists to
develop tests that confidently quantify the total amount of PFAS in any given sample. Additionally, the
complexity of the samples that need to be tested can add another layer of difficulty when it comes to
analysis – soils, foodstuffs and other matrices often require unique analytical approaches.
Despite these complications, in light of the growing volume of scientific evidence outlining links between
PFAS exposure and negative health effects, the ability to detect and characterize PFAS compounds adequately in a variety of sample types is key to safeguarding public health.3
PFAS as an environmental hazard
The commercial success and widespread use of PFAS compounds can largely be traced back to the need
for materials and coatings with high degrees of thermal and chemical stability – something that PFAS
compounds deliver due to the strength of their carbon–fluorine bonds.
This resilience and hardiness can be a double-edged sword; it also causes PFAS to accumulate in the
environment and makes them difficult to tackle using traditional remediation strategies.4
“PFAS have been used for many decades before the scientific community discovered that they were
harmful – and because PFAS are so persistent, they have built up in our bodies, wildlife, waterways, food
and more,” said Dr. Lydia Jahl, science and policy manager at the Green Science Policy Institute.
“That means we have relatively high concentrations of harmful chemicals all over the world without easy
ways to remove them.”
IDENTIFYING AND CHARACTERIZING PFAS COMPOUNDS 2
Article
Scientists are still determining the precise health impacts of PFAS pollution and their bioaccumulation in
human and animal tissues. However, epidemiological studies have demonstrated links between exposure
to specific PFAS and a number of negative health effects, including altered immune and thyroid function,
insulin dysregulation, kidney disease, cancer and adverse reproductive and developmental outcomes.3
The increased scientific attention and regulatory scrutiny given to PFAS in recent decades has led to the
development of several techniques and standard analytical methods that can be used to identify and
characterize specific PFAS, as well as determine the total volume of PFAS in a sample.
“There are common mass spectrometry (MS) techniques used to detect PFAS in a variety of environmental samples,” explained Jahl. “Other methods like total organic fluorine (TOF) will identify organic fluorine
in a sample, which is likely PFAS. More innovative methods like particle induced gamma-ray emission
(PIGE) spectroscopy, pioneered by Dr. Graham Peaslee at the University of Notre Dame, is a rapid screening method for total fluorine, which is a marker for PFAS but includes non-PFAS too.”5
Standard analytical methods for PFAS detection
To date, the US Environmental Protection Agency (EPA) has developed, validated and published three
standard methods (Method 533, Method 537 and its updated version Method 537.1) to be used for detecting and analyzing a total of 29 unique PFAS compounds in drinking water.6
Method 537.1 was first published by the agency in 2009 and has been updated as more PFAS with the
potential to contaminate drinking water have been identified. The method is effective for 18 compounds,
including the most notorious PFAS, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA),
as well as the common industrial PFAS replacement compound, hexafluoropropylene oxide dimer acid
(HFPO-DA).
Analytically, the method relies on passing a water sample through a solid phase extraction (SPE) cartridge that contains polystyrene divinylbenzene to extract the relevant PFAS analytes. Using a methanol
solvent, the compounds of interest are removed from the solid sorbent and analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS).
Method 533 is similar, also using SPE with LC-MS/MS, but with the addition of isotope dilution standards.
These isotopically labeled analogs of the method analytes in question make it easier to compare signal
ratios and intensity, improving the accuracy of the method.
In addition to these, the EPA is also in the process of developing another method, currently referred to
as “Draft Method 1633” for the detection of PFAS in non-potable water and other environmental media,
including soils or sediment. While the method is still only a draft as of December 2023, the proposed
technique would make use of SPE cartridge clean-up procedures for sample prep, followed by LC-MS/
MS in multiple reaction monitoring (MRM) mode. Again, the spiking of samples with isotopically labeled
standards is also suggested.
The EPA is also currently engaged in efforts to expand their list of standard analytical methods (SAMs)
to include PFAS testing on ambient air and emissions, as well as methods for more general techniques,
such as TOF analysis, that can quantify large groups of PFAS in various sample types.
The challenges of detecting PFAS compounds
While these standardized methods of analysis work well for their intended scope, PFAS continue to present challenges in detection that scientists must work to overcome.
IDENTIFYING AND CHARACTERIZING PFAS COMPOUNDS 3
Article
“Not every method can detect every PFAS,” Jahl said. “That means that scientists have to use a variety
of sample preparation techniques, expensive scientific instruments and good data analysis to measure
different PFAS. As a result, resources of academic scientists, government environmental protection agencies and others are often too limited to measure enough samples to find all PFAS contamination.”
“It also means that scientists don't measure all specific PFAS that are in the environment, especially as
the chemical industry is constantly manufacturing new PFAS – i.e. regrettable substitution,” she added, referring to the rise of compounds designed as PFAS substitutes. Though these compounds do not
fall under the PFAS umbrella, their broader environmental effects are uncertain and are still a concern
among environmental scientists.
Current forms of PFAS detection are also very resource intensive, adds Professor Timothy Manning
Swager, of the Massachusetts Institute of Technology (MIT).
“LC and MS are very limiting because the cost of the equipment is very high – more than a luxury car,”
he said. “In addition, the operation and sample preparation is very complex and requires a highly skilled
technician. It is very difficult to keep such skilled people in a repetitive job like running PFAS tests.”
Another important limitation is the relative lack of portable PFAS testing equipment. One of Swager’s key
research interests is in the development of chemosensors – sensors designed to detect specific chemical
signals – including the development of portable chemosensors that can detect PFAS in the environment.
“Localizing the sources of PFAS and the spatio-temporal distribution of the species is critical to understanding where the pollution is coming from,” said Swager. “It is also important at the household level to
understand if their water is clean. Our methods can be used for continuous monitoring of water to towns/
cities as well as periodic testing of water in homes or in environmental samples.”
“A fundamental advantage of a chemical sensor scheme is that it can be very simplified such that even an
untrained consumer can conduct the test,” Swager added.
Novel PFAS detection techniques
In the late 1990s, Swager invented a method of creating ultrasensitive fluorescence sensors using semiconducting polymers that are extremely efficient at absorbing and emitting light.7
This approach enabled
the creation of the portable, ultrasensitive Fido explosives detector that is used by the US military and by
major American airports.8
Now, Swager is applying the same innovative technique to develop portable sensors that can detect the
presence of PFAS in tap water.
“The ultrasensitivity is the result of the ability of our special polymers [to] allow for the efficient migration
of excited states in the materials,” Swager explained. “So, similar to an electrical conductor, our materials
are energy conductors. The advantage is that the excited states can visit up to 20,000 different potential
analyte – in this case, PFAS – binding sites.”
In a new paper, recently published in Angewandte Chemie, Swager and his former MIT colleague
Dr. Alberto Concellón report the development of a polymer-based detection technique that can detect
PFOA and PFOS in the micrograms per liter range – making it suitable for use with samples that have
been concentrated through SPE or directly in heavily contaminated regions.9
The polymer used in the new test can take the form of a thin film or nanoparticles, with fluorinated
sidechains embedded with fluorinated dye molecules. As the special polymer absorbs light, it transfers
IDENTIFYING AND CHARACTERIZING PFAS COMPOUNDS 4
Article
this light energy to the dye via an electron exchange mechanism, which causes the dye to fluoresce red.
However, if PFAS are present in the sensor’s environment, they will enter the polymer and displace the
dye molecules slightly. Even this nanometer-sized displacement is enough to disrupt the energy transfer,
and so instead of fluorescing red, the detector will instead fluoresce with the blue color that is characteristic of the polymer. The degree of this fluorescence change is proportional to the concentration of PFAS
compounds in the sample.
“… [O]ur materials behave as sponges for PFAS,” noted Swager. “The binding of PFAS to the materials
either enhances or prevents a new emission resulting from the transport of excited states to the PFAS
interaction sites.”
Fluorescent chemosensors are not the only novel approach being trialed for PFAS testing; other research
groups have reported using novel optical fiber sensor networks to detect PFOA in aqueous samples.10 Another study reports the successful use of a new three-dimensional-printed cone spray ionization (3D-PCSI) technique with ambient ionization MS in detecting 11 unique PFAS in the parts per trillion range.11
Collectively, whatever the specific analytical approach taken by these techniques, their end goal is the
same – to enable the efficient and accurate detection and measurement of PFAS in areas of interest.
Through the development of novel, rapid, on-site detection techniques and the adoption of highly accurate
quantitative standard methods, researchers and governmental bodies alike are better prepared to evaluate and tackle the difficulties posed by PFAS contamination.
References
1. PFAS chemicals overview. Agency for Toxic Substances and Disease Registry. Published November 1, 2022. Accessed
November 24, 2023. https://www.atsdr.cdc.gov/pfas/health-effects/overview.html
2. Per- and polyfluoroalkyl substances (PFAS). European Chemicals Agency. Accessed December 5, 2023. https://echa.
europa.eu/hot-topics/perfluoroalkyl-chemicals-pfas
3. Fenton SE, Ducatman A, Boobis A, et al. Per- and polyfluoroalkyl substance toxicity and human health review: Current
state of knowledge and strategies for informing future research. Environ Toxicol Chem. 2021;40(3):606-630. doi: 10.1002/
etc.4890
4. Darlington R, Barth E, McKernan J. The challenges of PFAS remediation. Mil Eng. 2018;110(712):58-60. PMID: 29780177
5. Tighe M, Jin Y, Whitehead HD, et al. Screening for per- and polyfluoroalkyl substances in water with particle induced
gamma-ray emission spectroscopy. ACS EST Water. 2021;1(12):2477-2484. doi: 10.1021/acsestwater.1c00215
6. PFAS analytical methods development and sampling research. United States Environmental Protection Agency. Published April 21, 2020. Accessed December 11, 2023. https://www.epa.gov/water-research/pfas-analytical-methods-development-and-sampling-research
7. Zhou Q, Swager TM. Fluorescent chemosensors based on energy migration in conjugated polymers: the molecular wire
approach to increased sensitivity. J Am Chem Soc. 1995;117(50):12593-12602. doi: 10.1021/ja00155a023
8. Ortiz C. The value of the modern research university: MIT as a case study. Presented at: Massachusetts Institute of Technology, October 1, 2012. Accessed December 10, 2023. https://web.mit.edu/cortiz/www/Education/AGSOrtizPublic.pdf
9. Concellón A, Swager TM. Detection of per- and polyfluoroalkyl substances (PFAS) by interrupted energy transfer. Angew
Chem Int Ed. 2023;62(47):e202309928. doi: 10.1002/anie.202309928
10. Pitruzzella R, Arcadio F, Perri C, et al. Ultra-low detection of perfluorooctanoic acid using a novel plasmonic sensing
approach combined with molecularly imprinted polymers. Chemosensors. 2023;11(4):211. doi: 10.3390/chemosensors11040211
Access This Article for FREE Now!
Information you provide will be shared with the sponsors for this content. Technology Networks or its sponsors may contact you to offer you content or products based on your interest in this topic. You may opt-out at any time.