Webinar Recap: New and Evolving PFAS Test Methods
PFAS have been around for decades and solving the contamination problem that’s been building up over the years is going to take a lot of smart people working on everything from detection to remediation. At Pace®, we’re focused on the detection part of that equation, so we have a front-row seat to the release of new PFAS test methods and the evolution of existing approaches.
To bring our customers up to speed quickly, I reviewed many of the available and emerging methods for detecting and measuring PFAS in a recent webinar. If you haven’t looked at test methods in a while, I think you’ll be surprised at just how much has changed in the last year. Here’s a quick recap of some of the methods covered:
EPA Test Methods 533 and 537.1 – These two drinking water test methods have been around for a few years, so pretty much everyone involved in the drinking water industry is familiar with them. Together, they can analyze for the 29 PFAS compounds included in the UCMR 5 unregulated contaminants list, so both of these methods will be required once sampling begins in 2023.
What is not as well-known in the industry is that the EPA has slated revisions to these methods over the next couple of years. As additional PFAS emerge as contaminants of concern, the agency is looking at the feasibility of expanding the targeted analyte list. This work is expected to be complete by the fall of 2024.
EPA Draft Method 1633 – Published in August of 2021, Draft Method 1633 is getting a lot of attention despite not having been finalized yet. This method can quantitate 40 compounds across a wide range of solid and aqueous matrices. Once validated, Method 1633 will play a vital role in the EPA’s efforts to study, monitor, and regulate PFAS in matrices other than drinking water, including both solids and liquids. In fact, the agency recently issued a memo stating that Method 1633 will be required for NPDES permitting even before the method passes the multi-lab validation phase.
DOD QSM B-24 – As we’ve discussed before on this blog, the DOD QSM (Quality Systems Manual) does not include a method per se. Instead, it is a set of protocols to be used for DOD projects. The Department of Defense (DOD) published QSM Table B-24 to refine Draft Method 1633 for DOD projects.
PFAS Screening Methods
The next couple of methods discussed are classified as “screening methods,” meaning they aren’t as precise as the methods discussed above, but they can be useful for performing quick, often less-expensive assessments to determine if further analysis is needed.
The primary reason for the lower precision/cost is the way samples are prepped for analysis. EPA Test Methods 533, 537.1, and Draft Method 1633 (as well as others not discussed) use solid phase extraction to prepare the sample; whereas the following two methods use direct injection.
Solid phase extraction – A sample preparation technique which involves passing a liquid sample through a solid sorbent to concentrate target compounds for analysis.
Direct injection – Samples are diluted 1:1 with methanol and then directly injected onto the instrument for analysis. Direct injection is only suitable for liquid samples.
- EPA Method 8327 – Published by the EPA in July of 2021 as a screening method, Method 8327 can analyze for up to 24 PFAS compounds in non-potable water samples. Since publication, the method has not gained much traction. One reason is because quality control challenges have cropped up for 9 of the compounds in the targeted analyte list.
- ASTM D8421 – This method was published by the American Society for Testing & Materials (ASTM) in December of 2021. It also serves as a screening tool for non-potable waters but can analyze for up to 44 compounds. In addition, ASTM D8421 includes the option to use isotope dilution quantitation, which resolves some of the QC challenges included with EPA Method 8327.
To recap, direct injection is only suitable for liquid samples, so neither of these methods can be used to analyze solids. They are also classified as screening methods, so neither are likely to be used for regulatory purposes in their current form. However, Method 8327 is a useful data collection method for the EPA as it seeks to better understand the extent of PFAS contamination in non-potable liquid matrices such as stormwater, runoff, wastewater, groundwater, and more. Both Method 8327 and ASTM D8421 may also be useful for businesses looking to assess potential liability issues related to PFAS contamination.
Not sure which method to use? Reach out to our Emerging Contaminants team.
Methods for Measuring Total Organic Fluorine
All of the above methods use mass spectrometry to measure the level of specific PFAS compounds in a sample. Another class of methods uses combustion ion chromatography (CIC) to measure the total of a group of compounds, in this case, organic fluorine. I won’t go deeply into how this method works, but if you’re interested in learning more, my presentation provides more detail.
- True-TOF® - This method was developed by Pace® to measure total organic fluorine in a non-potable liquid sample without extraction to a carbon media. Without the need for extraction, True-TOF can be a more reliable test than other methods, such as AOF (see below), because extraction efficiency is not an issue. True-TOF is also a low-volume test that only requires 10 mL of liquid matrix.
- EPA Draft Method 1621 – The EPA’s Draft Method 1621 belongs to a class of test methods designed to analyze total adsorbable organic fluorine (AOF) in a liquid or solid matrix. Pace® was selected to collaborate with the EPA for the single lab validation phase (now complete) and in the multi-lab validation phase (currently underway).
Draft Method 1621 requires an extraction phase, in which the sample is passed through a granular active carbon (GAC) cartridge. This is the first step in separating inorganic and organic fluoride compounds so that total organic fluorine can be measured. Again, I go deeper into the process in my presentation. This method can be used with liquid samples, and with a few modifications to the process, solid samples as well.
Which PFAS Test Method Should You Use?
In this post and in our webinar, we only touched on the latest evolutions in PFAS Test Methods. There are many more commercially available test methods, and the landscape will continue to evolve as existing methods are refined and new methods are developed. As I alluded to at the beginning of my post, this evolution is going to have to happen for our world to be able to address the PFAS contamination problem.
At the end of the day, which test method you should use depends on your unique situation. To over-simplify it a bit: Which matrices do you need to test and why? The Pace® Emerging Contaminants team (Paul, Kevin, Nick, myself, and others) are available to work one-on-one with you to help you assess the best approach. Reach out to us to request a consultation or a briefing for your organization.