Per- and polyfluoroalkyl substances (PFAS) are chemicals containing strong carbon-fluorine bonds that are used for many purposes due to their ability to resist grease, water, and oil. Of the hundreds of products PFAS can be found, some common examples include nonstick cookware, water-repellent clothing, stain resistant fabrics, and other household and lab materials.
These may be individual molecules, like perfluorooctane sulfonic acid (PFOS) or perfluorooctanoic acid (PFOA), or different chain lengths of polymerized materials. There are nearly 15,000 different PFAS molecules that have been identified. Due to the strength of the carbon-fluorine bonds, these chemicals don’t readily degrade and are persistent in the environment.1,2,3,4,5,6
While the human health effects of PFAS are not clear, animal studies have indicated growth and development issues. This is troubling because nearly all people included in a 1999 study by the Centers for Disease Control have detectable amounts of PFAS in their blood.
The potential hazards of PFAS are important to labs because their persistence may enable them to be present in any sample, and because of the need to protect lab staff from harm. As regulation increases around exposure to PFAS, labs will have greater responsibility to eliminate them from their equipment and tools and analyze for them to ensure their organization is not contributing to the problem. “An essential aspect of containing and characterizing PFAS is knowing where and how much of it is present in the environment, and that's predicated on having access to high-quality analysis.” explains Tarun Anumol, PhD, director, Global Environment Market, Agilent Technologies. “We are at the tip of the iceberg regarding PFAS; the list of compounds requiring investigation and analysis will undoubtably increase. It is also important to note that several newer PFAS compounds being discovered are smaller and more volatile, so they will require additional testing techniques to be able to analyze and completely characterize.”
Analyze or outsource?
Despite their prevalence, there are significant challenges in analyzing PFAS materials. “Because exposure to PFAS is linked to human health and environmental impact, it is important to measure these compounds accurately and precisely in various matrices,” says Oliver Burt, director of LC-MS/MS Core solutions at Waters Corporation. “Many regulations and exposure advisory limits require detection of various PFAS in the low ng/L (parts per trillion, ppt) or even pg/L (parts per quadrillion, ppq) ranges for samples from sources such as manufacturing plant discharge, local water utilities, landfill leaching, firefighting foam discharge, etc.” These very low levels of detection and quantitation require significant investment in instruments and human expertise.
Many labs have experience analyzing for trace contaminants and have the instruments, tools, and expertise to tackle PFAS analyses. In these situations, it will be important to learn from existing published methods and develop the appropriate methods and workflows to tackle PFAS analysis.
However, many labs don’t have the experience to readily move into PFAS analysis. In this case, the time, effort, and money required to develop these workflows and methods might be better dedicated to other strengths of the lab. The issues regarding PFAS analysis can be addressed by developing the right partnership with an external contract lab as an outsource partner. “Key things to ask about PFAS analysis are the price, turnaround time, the type of sample container, and the required clarity of the sample,” says Meera Neb, owner and president of TTI Environmental Laboratories. “Not everything can be tested for PFAS.”
Building a partnership with an external contract lab for PFAS can help save capital investment and eliminate the need to hire expert staff and spend significant time on developing new methods and lab procedures. It can often be significantly less expensive to rent rather than own these capabilities. Since there is significant demand for PFAS analysis, there are many different labs available with expertise in these analyses
A starting point for PFAS analysis
If the lab has the right expertise and instruments and wants to start PFAS analysis, the Environmental Protection Agency has published some methods for the determination of PFAS in water. A good place to start would be EPA method 537.1 that specifies solid phase extraction and liquid chromatography with tandem mass spectrometry (LC/MS/MS) analysis of 18 different PFAS analytes. Another method to consider is ISO 21675:2019. It also highlights the use of LC/MS/MS to deliver the required specificity and sensitivity. This method is focused on the linear PFAS isomers.
Of course, many more PFAS molecules exist and may need to be analyzed. “With the emerging interest around PFAS breakdown pathways in the environment, laboratories are looking to better understand what additional PFAS compounds are present in their sample,” says Toby Astill, PhD, director for Thermo Fisher Scientific’s Environmental Vertical Marketing.“To do this, they can leverage high resolution accurate mass (HRAM) mass spectrometry workflows with built in PFAS libraries. These libraries contain over 10,000 PFAS compounds, which allow more efficient data reduction that gives the analyst higher confidence in detection and annotation of suspect PFAS compounds.”
Before a workflow can be determined, the lab must understand if the samples in question are to be analyzed for specific PFAS compounds through a targeted analysis method or for any detectable PFAS compounds through an untargeted analysis. Here are the steps involved in a typical PFAS workflow for a targeted analysis:
- Collect the sample. Ensure the sample is collected and stored in PFAS-free containers.
- Concentrate the analytes using solid phase extraction (SPE).
- Separate analytes using LC
- Analyze analytes using MS. This can be LC/MS or LC/MS/MS depending on the required sensitivity of the analysis
Burt suggests that “deploying these technologies as a system solution into the laboratory can help to ensure reliability and reproducibility of results.”
If a sample requires untargeted analysis, it is often helpful to analyze the amount of fluorine in the sample prior to LC/MS analysis using fluorine adsorption followed by combustion ion chromatography. Comparing the results of a targeted analysis to the amount of fluorine detected will enable the lab to know if all of the fluorine detected is accounted for by the detected targeted PFAS materials. If not, the sample can be analyzed by HRAM to identify other PFAS materials in the sample.
If more specific PFAS workflows are required, LC and LC/MS vendors have them readily available on their websites. They also have application notes that can assist with developing methods specific to their instruments.
Reducing PFAS background
Since PFAS have become persistent in the environment and present in a wide range of products, it can be difficult to eliminate them from the lab’s work processes. Work carefully with vendors of equipment, tools, instruments, and consumables to find options that are PFAS-free. All of the common items, such as isolator columns, tubing, solvent lines, fittings, and vials can be obtained from vendors that are sufficiently clean to use in highly sensitive PFAS analyses.
Lab automation for PFAS
For labs that see many PFAS analyses, lab automation can help reduce the burden of tedious sample preparation. Automation can also improve the overall consistency and precision of these experiments compared to having them done completely by lab staff. With the growing importance of PFAS analysis, new automated sample preparation tools have recently been developed that are consistent with EPA 537.1.
Astill suggests that, “with laboratories experiencing increasing monthly PFAS sample volumes, automation is being leveraged to reduce sample turnaround time. An example is the use of automation technology to improve the sample preparation process where the offline manual SPE process can be automated for all four steps of SPE (conditioning, loading, rinsing, and eluting) to reduce solvent consumption, and improve recoveries and sample throughput.”
While analyzing PFAS can be challenging, lab managers have choices to address their organizational needs that range from seeking an effective outsource partner to utilizing experienced internal staff to getting support from vendors to start doing these analyses in-house.