1. Karla Buechler – Corporate Technical Director
The Analysis of Per and Polyfluorinated Alkyl Substances (PFAS) Challenges and Best Practices
Karla Buechler – Corporate Technical Director
Thank you
Good morning and good afternoon everyone and thank you for joining me today.
Todays webinar is TestAmerica’s introductory webinar on polyfluorinated alkyl substances which includes PFOS (perfluorooctane sulfonate) and PFOA (Perfluorooctanoic acid).
Let’s start with a quick look at the topics we will cover today.

2. PFAS - Outline Introduction to PFASs Analytical Best Practices
What are PFASs?
Chemistry Sources, Timeline
Exposure, Toxicity and Risk
Regulatory Review
Analytical Best Practices
Analytical Methods review
Why so much variability?
How do we reduce variability?
New In Line SPE Capability
Future Concerns – TOP Assay
Alternative chemicals – GenX
Capabilities and Questions?
For those of you who have attended a PFAS webinar in the past, the first half of the presentation is a review.
We will begin with what are PFASs.
Then cover nomenclature and chemistry in order to improve our communication with each other and our understanding of these chemicals.
We will look at the sources of PFAS to the environment, the historical timeline and how these chemicals are formed.
We need to understand routes of human exposure, the toxicity and risk of these chemicals and the current regulatory status.
Then we will change gears.
In the second half of the presentation our goal is to establish a set of analytical best practices and to introduce new topics.
We will look at the strengths and weaknesses of the existing published methods.
We will need to try to understand why there is so much variability in PFAS analytical results.
Next up we will look at TestAmerica Sacramento’s variability reductions steps.
The new material will include TestAmerica’s new capabilities, an In Line SPE technique, the TOP assay, and fluorinated replacement chemicals.
We will conclude with a discussion of future concerns and wrap up with a few minutes of Q and A.
So here we go.

3. Briefly - What are PFASs?
Class of synthetic compounds containing thousands of chemicals formed from carbon chains with fluorine attached to these chains.
The C-F bond is the shortest
and the strongest bond in nature.
PFOS and PFOA are fully fluorinated and the most common perfluorinated chemicals (PFCs).
Persistent and resistant to degradation Found in soil, air and groundwater..
PFASs are a class of synthetic compounds which contain thousands of chemicals. The basic requirement for entry into this class of chemicals is that the chemical have at least one fully fluorinated carbon atom.
This carbon-fluorine bond is the shortest and strongest covalent bond in nature. It is responsible for most of the unique and useful characteristics of these chemicals.
PFOS and PFOA are completely fluorinated, which means every hydrogen has been replaced with fluorine.
PFOS and PFOA were the PFAS chemicals produced in the largest amounts in the US.
These chemicals are extremely persistent and resistant to degradation in soil, air and groundwater.
Small amounts are found in the blood samples of humans and wildlife worldwide.

4. Chemical Structure Why is it Important?
Perfluoroalkyl Sulfonamido Amines
Perfluoroalkyl Carboxylate
Perfluoroalkyl Sulfonate
After a quick glance at the 5 chemicals shown here, you will notice that each chemical structure is similar in 2 basic ways.
First each consists of a chain of carbon atoms surrounded by fluorine atoms. This carbon chain backbone is present on the left side of the structures displayed here. This carbon chain backbone can have between 2 and 18 carbon atoms.
Second, a charged functional group is present at the end of the carbon fluorine backbone, is shown on the right side of the structures displayed and is typically a carboxylate or a sulfonate salt or an acid. PFCs with 8 or greater carbon atoms, including PFOS and PFOA, are called long chain PFCs.
The carbon chain portion of the molecule is responsible for the lack of degradation, lengthy stability and the bio-accumulation of these chemical because it is the inert portion of the molecule.
It is the charged functional group on one end that allows us to capitalize on the unique and desirable qualities of these chemicals.
So, how do PFAS get into the environment?
Perfluoroalkyl Sulfonamido acetic acid amine
Fluorotelomer Sulfonates

5. Primary Sources – Point or Direct
Released in large quantities from primary manufacturing facilities
Secondary Manufacturing – incorporation of PFC raw materials into industrial and consumer products
The use of AFFFs to fight fires is a direct pathway to the environment – (Connection to DoD)
PFAS are emitted into the environment from both primary and secondary sources
Let’s cover the primary sources to the environment first. These are the direct or point source routes to the environment.
A major point source or primary source for PFAS are the actual PFAS manufacturing facilities. These facilities had PFAS contaminated, water, waste and air emissions at their facilities that contaminated the environment surrounding them. In addition, these facilities had spills on-site and used local landfills for their solid waste streams.
The next primary sources for environmental contamination are the secondary manufacturing facilities. These are the industries that incorporated PFAS raw materials into industrial and consumer products. These industries included as primary sources are aerospace, construction, fire-fighting, food processing, household products, paper and food packaging just to name a few. Just as with the primary manufacturing facilities all of these facilities had water, solid and air emissions as potential routes to the environment also.
Lastly, the production, application and disposal of AFFF is a significant point source for PFAS. The unique characteristics of PFCs help the foam flow across burning petroleum, and they allow water to form a layer on top of the liquid petroleum, which cools the fire. In addition, PFCs help the foam seal in chemical vapors to prevent a fire.
Herein lies the PFAS connection with US Department of Defense sites. In 1966, aqueous film forming form (AFFF) was patented as a method for extinguishing liquid hydrocarbon fires. In 1969, the DoD issued a military specification, which included the requirement for PFOS in fire extinguishing agents.
So, there are thousands of primary sources of PFASs to the environment.
Let’s move now to the secondary, indirect or non-point sources.

6. Secondary Sources - Indirect
Commercial and consumer products have a finite lifetime.
Dispose to landfills
WWTP
Air emissions
Trace chemistry – transformation mostly degradation by-products (TOP Assay)
The secondary sources or indirect sources of PFAS to the environment are unique in that they include the use and disposition of industrial and consumer products.
As discussed earlier, the primary manufacturers of these chemicals present the direct exposure but it is the use and disposal of consumer products that defines the routes of secondary exposure.
PFASs are used in huge numbers of commercial products. They are used to repel oil and water from food packaging products, such a pizza boxes and microwave popcorn bags. They are used as fabric and upholstery treatments.
Each of these consumer products has a finite lifetime.
After we have consumed our food, that was wrapped in a water and oil resistant paper wrapping, we toss the wrapper in a garbage can. Ultimately, the spent solid consumer products end up in our landfills. The spent aqueous consumer products end up in waste water treatment plants or as direct emissions to the air.
Lastly, PFOA and PFOS are the end products in transformation and degradation chemistry. It is this important chemistry that is measured in the TOP Assay, which we will still discuss a bit later.
Here is a graphic of the exposure pathway.

7. Exposure, Toxicity and Risk
Major source of non-occupational exposure to humans is from food, water and air.
Human and wildlife exposure can continue even though the chemicals are no longer in use, due to persistence.
PFOS and PFOA have half-lives in humans ranging from 2 to 9 years, depending on the study.
 PFOA associated with liver, pancreatic, testicular, and mammary gland tumors in laboratory animals. PFOS causes liver and thyroid cancer in rats
PFOA and PFOS are likely carcinogenic. Pathways are being studied.
As we know, large amounts of PFOS and PFOA were released into the air, water and soil in and around fluorochemical facilities.
Hence, the levels of PFCs in the blood of people who work where PFCs are made or used are much higher than people who do not.
This pathway is defined as occupational and inhalation and dermal contact are the most common exposure routes.
PFC contamination of food and air is likely to be responsible for most non-occupational exposure.
Potential exposure routes include:
Eating fish from contaminated water bodies.
Eating crops grown in contaminated soils, particularly in agricultural areas that receive amendments of bio-solids from wastewater treatment plants.
Infant consumption of contaminated breast milk as the mother transfers her body burden.
Inhalation of house dust and direct contact with consumer products that have been treated with PFCs.
There are many routes for PFCs to biomagnify in the food web; and in fact polar bears have the highest concentrations of any wildlife or humans.
There are many published articles detailing the impact of PFCs on animals and most indicate that PFCs are toxic to animals.
They are readily absorbed after oral exposure and accumulate in the serum, kidney and liver. These studies indicate potential developmental, reproductive and systemic effects in laboratory animals.
When considering human health studies, more data is needed, but it is clear that there are negative impacts on human health.
The human body does not metabolize these chemicals and the half-life for these chemicals are in the years vs days or weeks for laboratory animals.
This lengthy half-life results in continued exposure that could increase human body burdens to dangerous levels over time.
Again, more data is needed, but it is evident in the literature that PFAS compounds are associated with several cancers in humans.
Let’s switch geers now and review the timeline of PFAS regulations.

8. Regulatory Challenges and New Developments
Lack of regulatory guidance for most matrices and most PFAS compounds
Wide variety of detection limits and analyte lists
Lack of published methods
What is Method 537M?
What are the ASTM Methods?
What is the ISO Method 25101?
There is an obvious lack of regulatory guidance for most matrices and most PFAS compounds. The EPA has issues a lifetime health advisory for PFOA and PFOS at 70 ppt in water.
There is a wide variety of detection limits and target analyte lists for federal and state regulatory agencies. Few of these levels are based in fact, with the exception of New Jersey as we saw earlier.
The area of most concern is a lack of published and multi lab validated methods.
What is Method 537.
What is Method 537M?
What are the ASTM Methods?
What are the ISO Methods (25101)?
Here is a brief regulatory timeline. 8

9. PFAS – Regulatory Timeline
When
Who
What Happened
1980s EU
Groundwater directive to prevent discharge of PFOS
2002
US EPA
Initiated voluntary phase out of PFOS 3M
Discontinued making PFOS (7 other makers complied)
2006
Announced 2010 (95%)/15(100%) PFOA Stewardship Program
2008
Canada
Regulated and prohibited PFOS imports to Canada
2009 UN
Stockholm Convention - adds PFOS to Annex B
2010
2010 PFOA Stewardship program - must reduce PFOA use by 95%
2015
Target elimination of PFOA by Dec. 31,2015.
May 2016
PFOS and PFOA life time health limits reduced to 70 ppt each or the total if both are present.
Sept 2016 NJ
DWQI proposed PFOA drinking water MCL of 14 ppt
The European Union took steps to prevent PFOS discharge into groundwater in the 1980s
In 2002, the US EPA initiated the voluntary phase out of PFOS. 3M and 7 other manufacturers complied.
In 2006, the EPA partnered with 8 chemical companies to launch the 2010/2015 PFOA Stewardship Program to reduce emissions and product content of PFOA and long-chain PFCs that break down to PFOA, including PFOS, by 95% by 2010 and to eliminate long-chain PFCs by The companies made great progress toward this goal.
In 2008, Canada regulated and prohibited PFOS imports to Canada and then expanded regulations to include the manufacture, import, use and sale of PFOS, its salts, precursors and long chain perfluorocarboxylic acids.
By December 31st, 2015 the final phase of the PFOA Stewardship program was applied. Again, great progress was made.
On May 25th of 2016, the US EPA established a lifetime health level for PFOS and PFOA at 70ppt each or in total if both are present.
In Sept of 2016 NJ proposed a PFOA drinking water MCL of 14 ppt.
Let’s look at the state regulations next.
What started happening in 2016?

10. What’s Up in New Jersey? (04/2018)
State
PFOA ppt
PFOS ppt
Comments
Source
Alabama 70
EPA
Alaska
400
ADEC
California
Prop 65
Proposed
OEHHA
Connecticut
PFNA, PFHxA, PFPeA, PFHpA
DPH
Colorado
PFHpA
Delaware
DNR
Georgia
Illinois
200
Iowa
Kentucky
NKWD
Maine
ME DEP
Maryland
Michigan
HB 5373 proposed 5 
MI DEQ
Minnesota 35 27
MDH
New Hampshire
DES
New Jersey* 14 13
NJDEP
New York
North Carolina
2000 NA
DENR
Ohio
Oregon
24000
300000
PFHpA, PFNA, PFOSA
Pennsylvania
70 (May lower to 6)
PA DEP
Rhode Island
Texas
290
560
PCLs for 16 PFCs
CEQ
Vermont 20
VT DOH
West Virginia
State and federal agencies are struggling with PFASs at various remediation sites across the country due to the lack of regulatory guidance.
The EPA, individual states, and the DoD are working hard to better understand the environmental and health implications of PFASs and to establish the much needed regulations.
Back in January of 2009, the US EPA Office of Water issued short term provisional health advisories for PFOA at 400 ppt and 200 ppt for PFOS.
Just recently, these levels were reduced to 70 ppt as we saw earlier.
Many states adopted the EPAs early guidance, including those states highlighted in green on the slide. I expect many states to reduce their health levels to 70 ppt in the near future.
Others have established their own levels, including New Jersey.
NJ has recently proposed 14ppt for PFOA and PFOS.
Why is this proposal so important?
New Jersey first became aware of PFCs in their drinking waters in 2006, so they are not new to the game.
It is the lowest proposed level to date. It was based on an extremely thorough review of Method 537 and method 537 Modified as performed at TestAmerica Sac and Denver and various other labs.
New Jersey was interested in what was detection limits were routinely achievable.
New Jersey is in fact proposing the lowest achievable level for both PFOA and PFOS. Their levels are also based on human toxicology studies.
This is a very dynamic situation so we need to continue to monitor it closely.
Let’s try and define what we mean by risk next.

11. Why are PFAS an Analytical Challenge?
Globally distributed
Present at low concentrations and high
Contamination and analyte loss at all stages of collection and analysis
Lack of authentic standards
Unusual physical and chemical properties
Lack of consensus “best” method for non-DW
Why are PFAS an analytical challenge?
These chemicals are ubiquitous and are found from pole to pole. They are found in most drinking water supplies and in most water bodies on the planet. They are typically found at ultra trace levels in drinking water. They are also found at gross levels in waste water and at DoD installations where AFFF was applied, stored or tested. This wide breath of contamination presents a challenge to sample collection processes and at the analytical lab. These sample streams must be kept separate. The risk of cross contamination is high.
It is challenging to prevent contamination. It is challenging to prevent contamination in the field from sampling equipment, bottle ware and the sample collection crews. It is also challenging to prevent contamination in the laboratory. Both groups must pay attention to details and QC systems before sample collection or laboratory testing begins.
Currently, there is a lack of commercially available authentic standards. The synthesis chemistry is difficult. For the few we have, even fewer of them have true second sources. In total we only have about 30 quantitative standards for these compounds.
The C-F bond gives these chemicals unusual physical and chemical properties. These chemicals are sticky. Many are non-volatile and they tend to stratify in aqueous matrices.
The biggest challenge is the lack of consensus regarding “Best” method for non-drinking water matrices.
Let’s briefly look at the analytical methods next. 11

12. How can we mitigate analytical variability?
Apply tandem mass spectrometry technology
Implement an isotope dilution quantitation scheme
Compensate for losses with matrix recovery correction
Share our knowledge
Invest resources in multi-lab validation
In the short term there are some steps we can take to reduce the variability and improve the quality of analytical results.
We can apply LCMSMS technology – we will look in more detail in a bit.
We can implement an isotope dilution quantitation scheme.
We can make certain labs are using the same MRM transitions.
We can make certain labs are applying the same algorithms for calculating detection limits.
We can make certain labs are measuring, mitigating and reporting background artifacts similarly.
In the longer term, we need all the bells and whistles, as we currently have for our historical methods and target compounds.
Including PTs, certification programs and consistent analyte lists so labs are not always playing catch up.
How does isotope dilution work?

13. Show Branched and Linear Error in PFOS and PFOA
B and L
L only
Standard
In the example here, PFOS is on the left and PFOA is on the right.
Method 537 states that branched and linear isomers should be reported when quantitative branched and linear standards are available.
So, on the left we have a PFOS standard with both branched and linear isomers, so both branched and linear isomers are summed in the sample data.
If we look at PFOA, only a quantitative linear standard is commercially available so we only report the linear isomer in a sample with a concentration of 0.99 ng/ml.
If we include both branched and linear PFOA then the true PFOA concentration is 1.20ng/ml.
In September of 2016 the EPA issued guidance to laboratories to include the branched peaks for PFOA. However, the only technical mix commercially available for PFOA, that includes branched and linear isomers is for qualitative use only and can not be used in quantitation. So, labs use it as a retention time marker for the branched PFOA isomers and labs must quantitate against a linear isomer only standard. We need a remedy as the response factors for the branched isomers are not equivalent to the linear isomers and our quantitation is biased.
In November the DoD QSM Version 5.1 incorporated similar language…only to retract it recently…hence lots of confusion regarding how to handle the isomeric forms of these compounds.
Additionally, this variability exists across other PFAS compounds and there are no branched standards at all.
Let’s move on to the next major cause of data variability, the lack of verifiable and demonstrated PT programs and look at some actual PT study data.
0.99 vs 1.20 ng/ml
Sample

14. Study Results - NMI PT 24 labs submitted results – 9 Passed
TestAmerica passed water, soil and fish tissue samples
Sample
Analyte
Sac Lab
Expected
Water A
PFOA
7.91
7.90
PFOS
3.23
3.00
Water B
9.01
10.8
6.81
6.50
Soil A
7.00
5.83
290
262
Soil B
14.2
12.0
23.5
22.0
Fish A ND
19.9
20.6
Fish B
51.4
50.5
49.2
53.7
Good News!!!
Lots a progress has been made in this category.
PT samples are currently available from a small number of sources which includes the National Measurement Institute.
Support funding was provided by the Austrailian Government Department of Industry, Innovation and Science.
There are also a few commercial providers, including Absolute Standards and ERA.
The study presented here is from NMI. This study was conducted from May to August of 2016.
126 labs were invited and twenty-four laboratories participated.
Six test samples were provided, 2 fish, 2 soil and 2 water samples.
24 labs submitted results.
TestAmerica Sacramento and 8 other labs returned satisfactory results for the matrices they submitted. The TestAmerica Sacramento generated data for all 3 matrices.
As you can see all results were passing. Point out fish results
We have concluded that based on the final report of all labs data, TestAmerica scored in the top 3 labs for these critical samples.
Moving on to Sample collection.

15. Sample Collection and Holding Time Studies
Samples should be collected in HDPE bottles fitted with unlined (no Teflon) polyethylene screw caps.
In addition, the sampler should avoid contact with fluoropolymers, aluminum foil, and food wrappers.
Samples should not be field filtered.
Samples must be shipped chilled
Limited HT study data
Most of the attention given to precision and accuracy in our industry is focused on lab data.
However, larger errors in sample results can occur from the improper collection and storage of the raw samples. In May of 2016, the published sample collection and sample collection guidance was inconsistent or incomplete.
Some progress has been made. There has been some education of sampling teams and there is some shift toward standardization.
Samples should be collected in high density poly ethylene bottles and every effort should be made to reduce the opportunity for contamination in the field. All sources of Teflon should be avoided during collection and storage. Polypropylene bottles should only be used when testing for the UCMR 3 list of PFCAs and PFSAs.
Samples need to be shipped chilled to the lab. The Trizma preservative is required for drinking water samples only.
Trizma is both used as a buffering agent and quenches residual chlorine. The primary source of loss in most samples is from a surface adsorption phenomenon.
Filtration should be avoided.
So, let’s look at how to manage artifacts.

16. Managing Artifacts
The field crew – personnel hygiene, clothing, food products, sunscreens and insect repellants
Sampling equipment – avoid fluoropolymer bailers, pump bladders, tubing, valves etc.
Sample collection – wash hands, wear nitrile gloves, do not filter samples, add field QC samples routinely
Avoid detergents
Avoid food or drink on-site
Limit visitors during sample collection
Of course the labs have to apply rigor to managing artifacts that result from the lab but let’s look at the sources of artifacts from the field.
The field crew and their leadership need to evaluate personnel hygiene, clothing, food products, sunscreens and insect repellants. Reasonableness applies here. We need to take a step back and confirm that our process is acceptable.
We need to run equipment blanks and other field QC to confirm that our sampling equipment is clean. We want to try to avoid fluoropolymer materials in our bailers, pump bladders, tubing, valves etc. If these materials must be used because they work the best or are the only options…then let’s again QC the setup and run additional equipment blanks when we have changed our process or replaced some parts.
Sample collection – wash hands, wear nitrile gloves, do not filter samples, add field QC samples routinely
It makes sense to avoid detergents and to avoid food or drink on-site
Additionally, it makes sense to limit visitors during sample collection
Again, reasonableness applies. There are no absolutes here.
What items should we use cautiously? 16

17. Managing Loss/Adsorption
Many PFAS are surface active, which cause them to stratify, adsorb to surfaces
Extraction type – whole bottle or subsample play a more significant role then material type
PFAS can adsorb to the filtration equipment. PFAS in the dissolved phase can also adsorb to the filter material
Unless the samples are analyzed immediately adsorption to glass vials may occur
Many PFASs are surface active, which cause them to Stratify, adsorb to surfaces, and aggregate, which results in their apparent loss from aqueous samples.
Losses are rapid, suggesting the losses are likely surface-driven and not due to diffusion into the container walls.
The extraction type – whole bottle or subsample play a more significant role them material type
Attention to container types and whole bottle rinsing with methanol is necessary.
Commonly used nylon membrane filter caused a complete loss of recovery.
Glass fiber filters are acceptable. Filtration is only applied when absolutely necessary after centrifugation has been determined to be insufficient.
TestAmerica uses glass fiber filters and rinses with methanol.
Lastly, it is necessary to manage loss by making significant modifications to the analytical instrument.
It is necessary to replace fluorocarbon components with poly ether ether ketone (PEEK) or stainless steel for the surfaces
contacted by the sample.
Now let’s look at how we can reduce variability. 17

18. What are Precursors and Why Do We Care?
Thousands of precursors used in industrial and consumer products
Some biotransform to make PFAAs
Some are fluorotelomers
Most are ionic, either positive, negative or both
Fate and transport – complex process
We already know that PFAS are a family of hundreds of synthetic compounds used in a wide variety of industrial and commercial products.
And that each contains carbon (C) chains with fluorine (F) atoms attached to these chains.
Polyfluorinated compounds are often referred to as “precursors” to the perfluoroalkyl acids (PFAAs), as they biotransform to PFAAs as dead end environmental products.
Current commercially available analytical methodologies are not capable of quantifying the full suite of PFAS compounds that exist in soil and groundwater. Many PFAS compounds in the soil and groundwater will progress through a biotransformation funnel that leads to PFAAs as dead-end daughter products. This presents a significant analytical chemistry challenge.
So, precursors are compounds, that may biotransform slowly to PFOA and other PFAAs over time.
We need a process to measure this biotransformation the TOP assay does just that. 18

19. What is the TOP Assay? A new PFAS sample preparation technique
Conceptually simple chemistry
Used with 537M not 537
Pre and Post results
Indicates unidentified PFAS
Quantified Transformation
The TOP assay is a new sample preparation or pretreatment technique.
We want to thank Dr. Erika Houtz, currently with Arcadis, for her valuable collaboration on this new capability as well as many of the diagrams you will see in the presentation.
TOP stands for Total Oxidizable Precursor Assay.
The chemistry is conceptually simple but the details are complex.
The TOP assay is a technique developed to quantify those difficult-to-measure and unidentified precursors to PFAA including PFCAs and PFSAs.
This is a sample pretreatment process of oxidation that mimics decades of aerobic biotransformation in a few minutes.
Samples are analyzed initially for a discrete list of analytes. Then they are oxidized utilizing the TOPs procedure to convert the precursors. Then they are analyzed again for the same list of discrete analytes.
The difference in the discrete analyte concentrations reflects the mass of precursors present in the sample.
We can’t determine risk for every compound - the TOP is a way to streamline the risk calculation and to reduce costs.
Are we getting closer to determining our total risk?
Unknown Potential

20. How Does it Work in the Environment?
Give me an example:
Low levels of discrete compounds are detected
High levels of discrete compounds are detected, which can include PFOA and PFOS
PFAA Precursors
Biotransformation
PFOA
PFOS
Outflow
PFAA
Inflow
Microbes attack the non perfluorinated parts (the polyfluorinated parts) of the PFAA precursor molecules making perfluorinated compounds as dead end daughter products.
An example of these environmental biotransformation processes is often seen in biological waste water treatment plants, where significantly more PFOA and PFOS are measured at the outflow than the inflow.
The increase is explained by the fact that many compounds enter the sewage treatment plant uncharacterized and are biotransformed to PFAAs of various chain lengths with PFOS and PFOA often being the only analytes assessed.
How does this biotransformation work in the lab? 20

21. TOP – How Does it Work in the Laboratory?
PFAA Precursors
OH•
PFOA + other PFCAs
85°C
85°C
The TOP assay rapidly converts our polyfluorinated precursors into PFAAs including PFOA, using a hydroxyl radical-based chemical oxidation method.
The oxidation reaction is detailed here.
The TOP assay replicates what micro-organisms in the environment would achieve after many years.
The end result is to provide a range of PFAAs which are detectable by LCMSMS.
The TOP assay quantifies the sum of PFAS that could be converted to PFAAs in the environment.
The TOP methodology has revealed that for AFFF-impacted sites, the existing analytical LCMSMS methods are only detecting an estimated 30% to 50% of the total PFAA mass present as PFAA precursors.
Erika F. Houtz and David L. Sedlak, “Oxidative Conversion as a Means of Detecting Precursors to Perfluoroalkyl Acids in Urban Runoff,” Environmental Science and Technology 46, no. 17 (2012):
Let’s take a closer look at a single precursor next.

22. PFCA Pattern – Me-FOSA Precursor
PFOA
Me-FOSA is a PFAA precursor.
In the environment Me-FOSA will transform to PFCAs including PFOA.
This graph is a post-treatment aliquot of a laboratory spiked control sample.
This aliquot was spiked with Me-FOSA only. The spike concentration was 500 ppt. The aliquot was oxidized and then extracted and analyzed by Method 537M.
As you can see, PFOA is the dominate PFCA, with a smattering of others.
The TOP assay does provide information regarding precursor carbon chain length.
Now let’s look at the pattern of a telomer sulfonate. 22

23. PFCA Pattern – 8:2 FTS 23 Again, this is a laboratory spiked aliquot.
This aliquot was spiked with 8:2 FTS at 500 ppt and the resultant pattern of PFCAs is very different from the Me-FOSA.
This time the dominant PFCA is PFHpA.
There are also significant contributions from several other PFCAs.
So, each pattern is representative of the precursor that was spiked.
Let’s look at an actual field sample next. 23

24. What Do the Results Mean?
TOP Assay measures total PFCA
Precursor
Pre - TOP
Post - TOP
% Oxidation
FOSA
32.68 ND
100%
MeFOSAA
19.38
EtFOSAA
18.83
6:2 FTS
31.69
8:2 FTS
26.37
PFCA
Pre – TOP
Total
PFBA
24.94
27.16
109%
PFPeA
23.38
28.55
122%
PFHxA
26.49
34.87
132%
PFHpA
23.10
25.14
PFOA
23.72
58.71
248%
Total 122
Total 174
This table lists 5 PFAS precursors on the top half and 5 PFCAs on the bottom half of the table.
You can see on the top half of the table that the PFAS precursors in the sample are present prior to oxidation. After oxidation they are ND, this is just exactly what we expect.
For example the precursor FOSA is present in the Pre TOP at ppb and after oxidation it is non-detect at 5ppt.
The Precursors are oxidized to the PFCAs.
This conversion is evident in the bottom half of the table. Please note that the PFCA results include the PFCAs native to the sample prior to oxidation.
The Pre TOP spike result for PFOA is ppb and the Post TOP result is ppb.
We see that each PFCA amount increases in the Post TOP.
This is a directional measure of your total PFAS risk at a site. Little or no change indicates few precursors of significance.
Whereas, a large change indicates a higher mass of precursors and a greater future risk.
Historically, the TOP assay has been limited to academic and research institutions.
TestAmerica Sacramento has commercialized this assay.
What conclusions can we draw?

25. What Conclusions Can We Draw?
PFAA precursors are present in environmental samples and many AFFF products
Implies treatment strategies must remove precursors and end points
Presence impacts our treatment strategies and our risk assessments
Potentially increases future risk as precursors are biotransformed
Presence impacts our decisions for AFFF formulations
AFFF manufacturers should reduce the content of PFOA etc.
TOP assay data can help us understand the potential PFAS risk.
It can also provide valuable details regarding the carbon chain lengths of the PFAA precursors present at a site.
This is very important as we transition away from the long chain compounds like PFOA and PFOS and toward shorter chain compounds.
We need a procedure that can measure our potential short chain precursor risk and now we have one.
Care must be taken when selecting treatment technologies so we don’t increase our PFCs concentration as an unintended consequence of treatment.
Lastly, the TOP assay data impacts decisions made by AFFF manufacturers and we see products made with telomerization products vs the messy chemistry in the ECF process.
Let’s look at fluorinated replacement chemicals next. 25

26. Fluorinated Replacement Chemicals
Since 2000, on-going industrial transition to replace LC PFCAs, PFSAs and precursors
Many alternative chemicals are in use – below regulatory radar
Unclear whether they are safe for humans or the environment
DuPont developed patented GenX technology - enables them to make fluoropolymers without PFOA
GenX is not a chemical it is a process
Since 2000, there has been an on-going industrial push to replace LC PFCAs, PFSAs and precursors as LCs are very persistent and very bioaccumulative.
Many alternative chemicals are in use – below regulatory radar. Due to concerns of business confidentiality, most of the information required to assess the safety of alternatives has not been published or made easily accessible to the public.
Hence, it is unclear whether they are safe for humans or the environment before they have been commercialized.
Several studies indicated that the shorter chain PFCAs and PFSAs are as persistent as their longer chain homologues.
In addition, several studies indicated that some of the shorter chains are more bioaccumulative than the longer chains.
We simply removed one chemical from a group of structurally similar chemicals and replaced it other chemicals in the same group but the problem was not solved.
There are significant data gaps that must be filled before we can make a safety determination.
As an example, DuPont developed patented GenX technology - enables them to make fluoropolymers without PFOA
GenX is not a chemical it is a process 26

27. Future Concerns We need a consensus “best” method.
Analyte lists are growing for discrete methods, may lead to forensics.
LC PFASs are being replaced by SC PFASs and little is know about the toxicity
On-going data variability must be improved
We need an effective field screening technique.
We need a consensus “best” analytical method and preferably one with a numerical assignment that does not have a 5 a 3 or a 7 in it.
Analyte lists were growing rapidly but we are seeing a stabilization. Most projects need the 6 UCMR3 compounds or a few more up to a total of 17 or 18. Some programs include analyte lists of 23 to 30 but it is not clear why all these additional compounds are included or if these extra compounds will remain important.
Next long chain PFCs are being replaced with short chain PFCs. We expect short chain PFCs to be safer, to degrade more quickly and we hope they perform equally. Little is known regarding their human toxicity so much more research is needed.
We need to continue to make progress reducing the data variability.
Lastly, we need an some effective field screening techniques.
That completes my presentation.

28. The Analysis of Per and Polyfluorinated Alkyl Substances (PFAS) Challenges and Best Practices
Questions 28