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Per- and polyfluoroalkyl substances (PFAS) are everywhere. They’re floating in the Arctic ocean. They’re sitting at the base camp of Mount Everest. They’re even, in all likelihood, flowing in your blood vessels.
This ubiquitous pollution was uncovered by dozens of researchers during separate studies over several years, and all of them came across the same hurdle: how does one actually test for PFAS?
The class of “forever chemicals” are still relatively young, only coming into existence during the 20th century. Academic understanding of the compounds eventually began to build in the 1990s, following decades of gatekeeping and lobbying from the chemicals’ two prime producers, 3M and Dupont.
Since then, a consensus has slowly formed on how to reliably quantify the pollutants – a consensus partly written by government scientists like Jessica Reiner.
Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials from microplastics to medical cannabis. Reiner is one of the agency’s leading scientists investigating PFAS analysis.
Technology Networks caught up with her to find out the considerations analysts should have when testing the forever chemicals, how to prepare a sample and what the future holds for this burgeoning field of chemistry.
Leo Bear-McGuinness (LBM):
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
When did you start researching PFAS?
Jessica Reiner, PhD (JR):
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
My story with PFAS actually begins in
graduate school. In the early 2000s I did research in a lab that was one of the
first places to measure PFAS in the environment. If you start looking back at
some of the papers, there were some original papers with Kannan's name on it;
one of the papers he did in 2003/2004 was [about] seeing PFAS in environmental
samples and animals throughout the whole world. That’s the lab I did my
graduate work in. I didn’t actually work on PFAS then, but I was in this lab,
so I was very much exposed to it.
When I finished that I went to get my postdoc, [then] I went to the US
Environmental Protection Agency (EPA) and found a group there trying to develop
chemical methods to measure PFAS. That was a great experience. I still get to
work with those guys all the time. But the focus of the EPA and the focus of
NIST are slightly different. I like to explain to people that making good
measurements is really important. If you get your cholesterol measured for a
doctor’s appointment, that measurement needs to be really, really good and high
quality, because the doctor is going to make a decision based on the data they
get back from the laboratory. So that’s sort of a NIST role.
The same is true in the PFAS realm if an environmental decision is going to be
made. Currently, we have drinking water regulations by the EPA. If the EPA is
going to do what they need to do with data on drinking water, that drinking
water data needs to be really good. So NIST really focuses on making sure those
measurements are of high quality. I really like NIST. What we do really helps a
lot of people.
So, I came to NIST after the EPA, and my focus when I came in 2008 was looking
at the suite of reference materials that NIST sells, and making measurements of
PFAS [listed] to make sure that those measurements were really good. I’ve been
lucky enough to be working on PFAS for quite a long time; I’ve seen it since
the beginning, when we had no chemical standards, to where we are today, where
we have measurement methods by the EPA.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
You’ve really been there from the beginning, then.
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
Yes. It was a very different world; we actually had to work with companies like 3M to get chemicals. Luckily, they were great partners and were happy, at that point in time, to supply the chemicals.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
How does one test for PFAS?
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
There are a lot of different extraction methods depending on the material you’re looking at, but when you start moving over to the instrumental side of things, for the most part, we use liquid chromatography (LC) with either tandem mass spectrometry (MS) or high-resolution mass spectrometry. That’s usually the main way people measure them, especially the PFAS that people see in the news a lot – PFOS, PFOA, things like that. There is a newer push to start measuring PFAS in the air using a technique like gas chromatography (GC) coupled to mass spectrometry.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
Sounds like a promising new avenue.
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
We have only done very little research as of right now. There are only a few volatile PFAS that you can actually purchase as chemical standards. But the work that we have done, they ionize with GC and you can get some nice separation. I do know that American Society for Testing and Materials (ASTM) is working on a volatile PFAS method; EPA is working on a volatile PFAS method, or might even have a draft method already available on their website. Unfortunately, we haven’t done enough for me to talk about any information we have. That being said, we are going to look at some of our existing reference materials and try and measure the volatile PFAS in them. We’ll take the methods that we develop here that we’re comfortable with, and then, hopefully in the future, add values of this volatile PFAS to something like our house reference material, so that it could be useful for people to use when they’re developing methods.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
Some labs use combustion ion chromatography (CIC) to measure PFAS, don’t they? Is that something that you use at NIST, or is it more of a rare test?
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
It’s not necessarily rare. CIC can measure total fluorine and, depending on what you do, can also measure total organic fluorine, but you have to do some things on the front end, so I don’t do it.
That gets into a very different question of what people define as PFAS. Is total fluorine total PFAS? I don’t know. Is total organic fluorine total PFAS? It depends on a person’s definition of what PFAS actually is, and that is definitely up for debate across the planet, even within the US, depending on the agency.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
So, the main method for testing is LC. What considerations should analysts have for this technique?
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
We’ve known since pretty much day one that when an LC instrument comes to you there is probably a background of PFAS in it. So contamination, even in a brand-new instrument, is potentially a thing, and can have you overestimate concentrations based on the contamination. We have an older instrument that we’ve been using for a long, long time, and we did not have a background of one specific compound, the heptanoic carboxylic acid. We changed a degasser, and, lo and behold, my background signal for this heptanoic carboxylic acid – so, fully fluorinated – increased tenfold. So, something that was used in the making of the degasser is adding contamination to my analysis. That is a big consideration.
We have luckily learned that we can put in what we call a hold-up column right before you inject your sample. That hold-up column can hold on to some of that PFAS a little bit longer, so it'll elute on your actual analytical column a little bit later. So you’re delaying it before you inject your sample. You can see the interference, but at least it doesn’t interfere with the signal coming from your sample. So that’s a consideration, especially on the LC side; background contamination from the instrument can lead to [readings] higher than it might be.
We also run into issues depending on the materials you’re analyzing. If they’re really short chain PFAS, some of these things have a multiple reaction monitoring (MRM) transition in the mass spec. That’s when the parent and the daughter ion are actually very similar to things that may occur in nature. So, again, you can overestimate concentrations. A good example of this is a bile acid that interferes with one of the transitions to measure PFOS. Analytically on the column, the bile acid could potentially co-elute with PFOS if in the mass spec. On the detection side of things, one of the transitions you use to measure PFOS also increases with this because it has the same transition. So, chemical interferences are also potentially a big issue.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
What considerations should analysts have during sample preparation?
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
The EPA does have methods out there that are available, so that is a great place to start. I also was lucky enough back before EPA had methods to do what we call a round robin study, or an interlaboratory study, where I sent the same sample to all the PFAS researchers – which was not that many at that point in time – so we knew the material was homogeneous. I asked all those researchers to use the methods that they were already using in their lab for extraction, and then I was able to compare all the data from the different analytical extraction methods that people were using. What ended up coming out of that paper was that, for the most part, people were using something like KOH methanol – basic methanol and some sort of leaky anion exchange cleanup. Their measurements looked very similar to measurements made with an acetonitrile type of extraction and then solvent exchanging to methanol and cleaning up with some sort of graphite carbon.
So, the methods were comparable. Also, we started getting data for the reference materials that NIST sells. These are products that anybody can purchase, and they actually have value assignments for different PFAS. So, I say, if you’re developing a method in your laboratory and you use this reference material, you should get this number plus or minus whatever that uncertainty is. If you know your method is working well, and you can trace it back to that reference material that you purchased at NIST, this is the data I get. I can show that it’s working well. So, there are a lot of different extraction methods that work and are comparable.
LBM:
Science Writer & Editor
Technology Networks
Leo is a science writer with a focus on environmental and food research. He holds a bachelor's degree in biology from Newcastle University and a master's degree in science communication from the University of Edinburgh.
What does the future hold for PFAS analysis?
JR:
Dr. Reiner is a research chemist at the US National Institute of Standards and Technology (NIST), a government agency that validates and improves scientific testing standards for a variety of materials.
There are going to be new compounds. We’re finding with these AFFFs, those aqueous foam forming foams, a large component are cationic and zwitterionic PFAS. When most people think of PFAS, they’re thinking of those anionic PFAS – PFOS or PFOA. Cationic PFAS, at least with AFFFs and maybe soils that were contaminated with that, might be of bigger importance, and they’re not in standard methods as of right now. So, I think measurements of those are going to be important in the future. And then there’s high-res mass spec. So, something NIST has been working on with the Department of Defense and a bunch of different universities is a database for high-resolution mass spec data of PFAS to help identify unknown PFAS better. We actually have this database; it’s freely available; people can download it. So, if you’re doing high-res and you see something in there that you say, “OK, this is fluorinated. We know this is a PFAS. Let’s check the NIST database and see if it’s been identified before.” If it has, maybe that gives you better confirmation of some newer compounds that that we don’t have standards for yet but might be important to measure in the future. If it’s not in the database, you can contribute that information to the database, so that if other researchers see it we can understand more of the PFAS story, instead of just PFOS, PFOA – the standard set of chemicals that we measure.
I think there’s been a lot of work on the forensic side of things and trying to identify sources. Something like this database could be useful for those unknowns.
