What you need to know about PFAS and PFAS analysis
What are PFAS?
More than 4730 compounds(1) belong to the group of PFAS (which stands for per- and polyfluoroalkyl substances) that have been produced since the 1940s. Since these compounds do not originate from nature, the global pollution is the result of human activity. All PFAS are of anthropogenic origin. PFAS are "forever chemicals", chemicals that are very persistent in the environment and in the human body.
General structure of per- and polyfluoroalkyl substances (PFAS)
PFAS are organic compounds with a carbon chain in which hydrogen is substituted by fluorine. The carbon-fluorine bond is very strong which makes them “virtually indestructable“. The molecular structure of the PFAS provides them with non-sticky and tensid-like characteristics (because of their hydrophobic, lipophobic chain + hydrophilic head).
There are polymers and non-polymers. Typical polymers are fluoropolymers, side-chain flurorinated polymers and perfluoropolyethers. Typical non-polymers are perfluoroalkyl acids (PFFFAs), perfluroalkane sulfonyl fluorides (PASF), perfluroalkyl iodides (PFAIs) and per- and polyfluroalkyl ether (PFPEs) based derivatives(2).
Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) have been the most produced and studied of these chemicals.
To cut a long story short: there are many different substance groups that need to be analyzed!
Where are PFAS used?
They are commonly used because of their non-sticky and tensid-like properties for various purposes:
- Textiles, textile coating, e.g., seat covers, carpets, outdoor clothing
- Fire extinguisher foams
- Food packaging, e.g., pizza cartons, paper cups
- Paper finishing
- Fibre coating
- Building material, e.g., water resistant lacquer
- Further consumer products, such as: furniture, polishing and cleaning agents and creams
How do PFAS find their way into the environment and the human body?
Per- and polyfluoroalkyl substances (PFAS) have been manufactured for more than 80 years, but health effects were neglected for a long time. In September 2020, the European Food Safety Authority (EFSA) published a new health risk assessment related to the presence of PFAS in food(3). This is the first EFSA expert opinion in which, in addition to PFOA and PFOS, other PFAS were also included in the exposure assessment and health risk assessment.
PFAS are emitted into the environment by different pathways. For example, exhaust air from industrial sources can contain PFAS and thus are dispersed into nearby ground and water bodies. Rain and snow, for example, can eventually carry them from the air into the soil and surface waters. Particle accumulation can even cause them to travel long distances through the air. PFAS are therefore also found far from industrial production sites and human living areas, such as in sediments from the Bering Sea to the Arctic(4/5). Through volatilization from products (evaporation from carpets or home textiles treated with soil-repellent agents) or from waterproofing sprays, indoor air can also be contaminated.
Soils can also be directly contaminated, for example by firefighting foams. With the uptake of PFAS from contaminated soils and waters in vegetation and their accumulation in fish, these substances enter the human food chain. Consequently, humans absorb PFASs from the environment through food, water or air.
These "forever chemicals" also find their way into wastewater treatment facilities from household sources. They then enter surface waters via treated wastewater or remain in sewage sludge. The sewage sludge, in turn, can be used as fertilizer in agriculture, and then over time these chemicals eventually leach into the groundwater. Once there, some of the precursor compounds are transformed into the persistent PFAS.
The special SPE phase – CHROMABOND PFAS
Over the years many different PFAS were developed. Now, they are found in the environment (water, food, soil, animals and humans) and their problematic health effects come into play.
The challenge is that current analytical methods are limited.
To tackle this challenge, we developed a special phase for the enrichment of a broad range of PFAS which provides good reproducibility and high recovery rates.
This is possible due to the different interactions the sorbent combination offers. These interactions are recommended by DIN 38407-42, EPA 537.1 and 533 guidelines.
Our CHROMABOND PFAS is a polymer-based combination phase which contains a weak anion exchange functionality. The combination of different SPE phases makes it possible to use various interactions (dipole-dipole, ionic, hydrophobic, H-bond).
CHROMABOND PFAS provides several advantages
- Solution for various PFAS substance classes
- > 28 PFAS can be enriched
- Sorbent retention mechanisms according to DIN 38407-42, EPA 537.1 and 533 guidelines
- High capacity
- High recovery rates
The special HPLC columns: NUCLEODUR PFAS and NUCLEODUR PFAS Delay
NUCLEODUR PFAS, 3 µm HPLC columns provide a solution for analyzing PFAS substances.
These columns show a high batch-to-batch reproducibility, are specially batch tested for PFAS analyses and are very well suited for LC-MS due to a low bleeding characteristics.
The NUCLEODUR PFAS Delay column provide high retention for PFAS compounds and are used to retain PFAS contaminants from the HPLC system, which could otherwise falsify the sample to be analyzed. For this purpose the NUCLEODUR PFAS Delay column is connected in flow direction between the mixing vessel and the sample injector.
PFAS analysis - solutions from MACHEREY-NAGEL
PFAS analysis performed on MACHEREY-NAGEL products according to official methods like EPA and DIN
EPA 533: The enrichment of PFAS using the SPE column CHROMABOND HR-XAW and subsequent chromatographic separation on a NUCLEODUR PFAS analytical HPLC column: PFAS analysis according to EPA 533
EPA 537.1: The enrichment of PFAS using the SPE column CHROMABOND HR-X and subsequent chromatographic separation on a NUCLEODUR PFAS analytical HPLC column: PFAS analysis according to EPA 537.1
Further Application Notes related to PFAS analysis:
An excerpt on the regulations and monitoring of PFAS
Within the European Union (EU), Germany, Sweden and other EU member states have already started to regulate the PFAS problem several years ago. For example the Stockholm Convention has listed in 2009 the perfluorooctanesulfonic acid (PFOS), its salts and PFOSF as persistent organic pollutants (POPs)(6) and the Water Framework Directive lists PFOS as a priority hazardous substance(7).
In the United States, continuous regulatory activities are being implemented by the U.S. EPA and other initiatives. These include:
- PFAS Action Act(8)
- US EPA PFAS Plan(9)
- US EPA Commitment to PFAS Drinking Water Standards with SDWA(10).
Many institutions worldwide are working on global monitoring for PFAS. For example, a guideline on this topic was developed in 2015(11) with active participation from China, Switzerland, Canada, Japan, Fiji, Kenya, Uruguay and other countries.
However, there are still nations that are not participating in these efforts or have not implemented PFAS regulation. For example no PFAS substances are regulated in India(12).
As toxicological information and additional PFAS compounds become identified in the future, further directives, restrictions, and regulations will be issued over time.
This pollution will therefore affect us all for generations. Chromatographic analysis will help us quantify the impact and make monitoring possible.
Not all PFAS have been banned yet. This is due to, among other things, the large number of substances that belong to PFAS. A complicating factor is that their identities and uses are only partially known. The regulation places high demands on the authorities. A ban is a complex and time-consuming matter because, among other things, a suitable substitute (substitutability) is not yet possible for all applications in some cases. This concerns, for example:
- Still an indispensable component of extinguishing foams for large fires
- In special technical protective clothing
- In some medical devices
Therefore, the authorities initially regulated only those PFAS that were detected in the highest concentrations in the environment and whose effects on the environment or human health could be justified.
The regulated substances were partially replaced by other PFAS that were not yet regulated. Less or no information was available on their hazardous properties, so their need for regulation was initially unclear. However, in recent years there has been increasing evidence that the entire group of PFAS is problematic from an environmental perspective. As a result, regulators have begun to consider a comprehensive ban on all PFAS.
The major challenge is to identify those uses that require an exemption because, despite their problematic properties, their use is considered indispensable to society as a whole.