Per- and Polyfluoroalkyl Substances (PFAS testing methods are still emerging and are rapidly developing. As measurement techniques become more accurate and sensitive and as regulatory agencies focus their efforts, resulting regulations will affect businesses across many industries that manufacture, use, and dispose of PFAS.
The current methods that test for PFAS can detect several hundred chemicals in water and soils. As the use of these chemicals has expanded over time, the total list of PFAS chemicals has swelled to include more than 6,500 different species, leading to a potential improvement in testing capabilities and the need for refining analytical target lists.
Testing for PFAS in the Air
A standard, reliable method for detecting and monitoring PFAS in the air has not yet been developed. Researchers aren’t yet positive about the relative amount of PFAS being emitted as particles or as gases, and what levels to monitor for. As the U.S. Environmental Protection Agency (EPA) states in the National PFAS Testing Strategy that was released in October 2021, “most of the hundreds of PFAS currently in commerce have limited or no toxicity data,” making it challenging to identify which chemicals to look for. Both these considerations figure into the development of new measurement methods.
When considering methods for detecting PFAS, users can take a screening or a speciated approach.
- A screening approach uses a broader technique that identifies a common characteristic (element or functional group) shared by multiple chemicals within a class of compounds. This method does not identify the amount of individual chemicals present within a sample.
- A speciated method looks for specific chemicals in a sample and quantifies the proportion of each chemical that is present.
Testing development must also consider methods for measuring ambient and point source emissions.
- Ambient measurements may be used to measure air quality throughout a community located near a facility that manufacturers or uses these chemicals. Currently, no methods exist for this application.
- Point source emissions are used to quantify what is being emitted from a single source, such as a stack at a facility. Currently, EPA Other Test Method 45 (OTM-45) has been released for use in source testing for PFAS compounds.
Current Testing Methods
Screening methods are often used as a first step to obtain non-speciated information by analyzing a common element shared by PFAS compounds. This helps to guide further investigation. An example of this is total fluorine analysis, which measures the amount of fluorine present in a sample to infer information about PFAS concentrations.
The next step is to test for specific target compounds. EPA-validated speciation testing methods for PFAS in soil and water were released in August 2021 and would be the place to start.
One of those methods for soil and water is Method 1633, a testing procedure that uses Liquid Chromatography-Mass Spectroscopy (LC-MS), which is an offline technique that analyzes samples in a lab.
- Liquid Chromatography separates samples into different components based on interactions with stationary and mobile phases.
- Mass spectrometers convert compounds to a charged, or ionized, state and categorize them based on their mass-charge ratio.
The combination of these two techniques can detect individual PFAS chemicals in soil and water that are extracted into a liquid state.
No ambient detection methods currently exist for PFAS. However, as noted previously, OTM-45 has been released for use in point-source testing. This method is based on previous source test methods and uses LC-MS to measure gas samples collected into a liquid phase with the use of an impinger.
Emerging Real-Time Techniques
In contrast to established testing methods that use offline laboratory analysis, emerging technologies are attempting to enable real-time, on-line sampling of PFAS breakdown products, such as the fluorotelomers class of compounds. One such technology combines a ramped thermal desorption procedure with cavity ring-down spectroscopy to provide high-sensitivity measurements of select PFAS compounds.
As specific PFAS compounds of interest are further identified, often on the basis of increased understanding regarding their toxicology and presence in the environment, the application of these emerging technologies will increase, and air monitoring regulations are likely to follow.
One of the biggest additional considerations for PFAS testing regardless of the technique is cross-contamination. PFAS chemicals are present in water, soil, clothing, and even the Teflon tubing that is commonly used in scientific instrumentation. Obtaining a clean sample to test is a real challenge. As a result, measurement techniques need to be extremely sensitive in order to detect small differences in PFAS levels.
PFAS measurements are complex, but as understanding of the intricacies of these compounds increases, research will continue to drive new monitoring techniques and regulations. Businesses in all industries related to the lifecycle of PFAS should prepare for new developments.