Unraveling the Impact of PFAS

Current estimates suggest that there are more than 4,700 per- and polyfluoroalkyl substances (PFAS) in existence, belonging to more than 200 different use categories. The extreme chemical stability of PFAS has led to their inclusion within non-stick cookware and firefighting foams, for example, as well as within common laboratory materials, such as sample preparation consumables and tubing.

In recent years, concerns have been raised over the accumulation of these compounds in the environment, leading to increased regulation and the need for more accurate and precise PFAS testing.

At analytica 2024, Technology Networks spoke with Dr. Susanne Soelter, field application specialist at Agilent, to learn more about the impact of PFAS and the challenges that come with PFAS testing.

Alexander Beadle (AB):  Could you give me a little bit more background on the impacts of PFAS and why they are such an important chemical class to monitor?

Susanne Soelter (SS): I'm a chemist and I’m an analyst, and from this perspective, PFAS have a lot of useful properties – and they are used nearly everywhere. When they were introduced, everyone was quite happy with what they could do, so nobody thought about what would happen with them in the future. We have a lot of products containing PFAS, we have a lot of processes that need PFAS for production and so on.

Because of this, over the last few years, a lot of PFAS were released into the environment, and now we see that they stay there. They are quite stable and can be found nearly everywhere. This is a real concern because some of them don't seem very healthy. Because of this we have to analyze them to make sure that products are safe, food is safe, water is safe and so forth.

AB: When it comes to this testing and environmental monitoring, are there any notable challenges that need to be overcome – or that have been overcome?

SS: I think there are several challenges, as always. One, of course, they are everywhere! And so we're talking about PFAS-free consumables and PFAS-free conversion kits for instruments, so that in the end you are sure that the value you report is really coming out of your sample and not being introduced somewhere during the analysis process.

Of course, if we want to quantify, we need good analytical standards, and we don't have these for each and every PFAS compound. In addition to these analytical standards, we also need labeled standards; PFAS are tricky, they tend to stick on surfaces and so you have to have these internal standards to compensate for this behavior.

Additionally, we have PFAS regulations all over the world, but they are not equal – what is being done in Europe might be different from what we do in the United States, and even the United Kingdom has different regulations to the European Union. So when you're doing these analyses, well, you can stick to your country or you might want to broaden it up.

And then there are also a whole bunch of PFAS compounds that we do not know very well. We know they are out there – but we don't have any standards, we don't know their structure. We have to analyze them as well and see if they are of importance.

AB: What sort of methods are being used to study PFAS?

SS: If you look at routine applications – for the compounds written into the most regulations – this is mainly liquid chromatography coupled with triple quadrupole mass spectrometry (triple quad LC-MS). Because these compounds largely ionize very well, they are very easy to catch with LC-MS with very low detection limits.

But of course, as I’ve said, we have a quite broad range of PFAS and some do not ionize with LC-MS, so we would then use other techniques like, for example, gas chromatography-mass spectrometry (GC-MS).

Or perhaps we want to screen for the unknowns, so then we have to go to other instrumentation like high-resolution mass spectrometry (HRMS), quadrupole time-of-flight (Q-TOF) mass spectrometry or maybe inductively coupled plasma mass spectrometry (ICP-MS), which with a little trick can detect all compounds which have fluorine in them.

AB: In addition to the so-called “legacy” PFAS that we do have extensive research and documentation on, there are also the “emerging” PFAS that we know much less about. Do these emerging PFAS present any unique challenges when it comes to analysis?

SS: It really depends. If I imagine an analytical lab, for example, they have to earn money with the analyses they are doing, and so what they like to have is a “one-method-fits-all” setup. If you broaden up your suite of compounds that you have to analyze, maybe this is not possible anymore. Because some of these compounds, maybe they work with LC-MS but you need other conditions to ionize them, maybe one ionizes in negative mode and one in positive mode – which is not a problem necessarily, but maybe you need other solvents to have the same sensitivity for the positive mode and for the negative mode. And then you have some that do not ionize easily at all, so you would need to go to GC-MS with them.

So yes, for some it is a challenge. For others, they are still similar – they are just new compounds. We need standards, we need new labeled standards, but they fit into the overall analytical package. And so for these cases, I would say no, they are not a problem, you just add them to your method.

AB: Are you aware of any notable advances or research efforts taking place with regard to PFAS analysis?

SS: There is a big focus on software for untargeted analyses. Because you collect so much data with untargeted analysis, you cannot manually go through each and every mass spectrum. You need good software to analyze those data, and I think this is an important trend that we will see – having the software that can cope with these data to give fast answers.

Dr. Susanne Soelter was speaking with Alexander Beadle, Science Writer for Technology Networks.

About the interviewee:

Susanne Soelter started her career as a product specialist for LC-MS at Varian in 2004.

She has remained loyal to LC-MS since then. In her current position as a Field Application Specialist, she develops new methods in the Agilent laboratory in Waldbronn and supports customers on site. Her focus areas are environmental applications and food analysis.

Susanne studied chemistry in Hamburg and received a doctorate degree in organic chemistry from the University of Hamburg.