A Conversation with Madison L. Williams on Volatile PFAS and Automated Microextraction

 At the University at Buffalo, Madison L. Williams (Ph.D. candidate, Gionfriddo Group) is at the forefront of this analytical challenge. Her recent work, published in Analyst and highlighted in our latest Application Note, provides a critical comparison between traditional SPME Fiber and the robust SPME Arrow for trapping these elusive compounds.

We sat down with Madison to discuss the mechanics of this "forever cycle," her journey from organic synthesis to analytical chemistry, and how automation helps to optimize complex extraction methods.

Question 1. Your work in the Gionfriddo Lab at the University at Buffalo addresses some of the most persistent environmental contaminants of our time. What originally drew you to analytical chemistry, and specifically to the challenge of analyzing PFAS?

I didn’t start out as an analytical chemist; rather, my undergraduate research was rooted in organic synthesis. During my senior year as an undergraduate, however, I was hired by a regulatory laboratory to analyze water samples for a range of analytes, including ammonia, phosphate, nitrate + nitrite, and chloride, using established EPA methods. While I was generally aware of soil and waterway contamination by anthropogenic chemicals, observing the concentrations present in certain samples firsthand was eye-opening. That experience shifted my perspective and motivated my interest in analytical chemistry, as I wanted to better understand how to detect and analyze these analytes. PFAS represented a natural progression of this interest. Due to their ubiquity across environmental compartments and their known detrimental impacts, there is an essential need to expand their ‘toolbox’ for analysis. The Gionfriddo laboratory has provided the opportunity to pursue this focus.

Question 2. In your research, you emphasize that while ionic PFAS (like PFOS and PFOA) get the spotlight, neutral volatile precursors are often overlooked. Why is it so important for environmental monitoring to shift its gaze toward these neutral precursors, and why have they historically been so difficult to analyze compared to their ionic counterparts?

It is not a matter of shifting its gaze, but of opening both eyes to the PFAS problem. Ionic PFAS represent a portion of overall PFAS emissions; if neutral precursors are not accounted for, the totality of PFAS sources will never be fully understood. In general, neutral precursors, such as fluorotelomer alcohols (FTOHs) and sulfonamides (FOSAs) are more volatile, mobile, and readily exchanged between indoor materials, air, dust, and the outdoor environment. Consequently, these compounds play a disproportionate role in long-range transport and the delayed formation of persistent ionic PFAS. Beyond serving as upstream contributors to legacy ionizable PFAS in the environment, neutral precursors also represent a significant and often underrecognized pathway for human exposure.

Despite this relevance, volatile precursors have historically been understudied, in part because conventional sample-preparation approaches developed for ionic PFAS are not readily applicable to neutral precursors due to their (1) lack of charged functional groups, (2) increased volatility, and (3) the absence of standardized analytical methodologies. Moreover, while liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS) is routinely employed for ionizable PFAS, it faces inherent limitations for neutral and short-chain precursors (e.g, FTOHs). Including ionization suppression from buffered mobile phases and the poor ionizability of PFAS with high fluorine-to-carbon (F:C) ratios, and, critically, the volatility of certain compounds, which can hinder retention and quantification.

Question 4. Your data suggested that competitive adsorption begins to occur at extraction times longer than 35 minutes, where volatile compounds like 4:2 FTOH are displaced by higher-affinity analytes. How does this finding change the way researchers should approach optimizing extraction times for multicomponent mixtures?

Our data indicated that for multicomponent mixtures, when using an adsorbent type of extraction phase (e.g., DVB/C-WR/PDMS), competitive adsorption for the more polar hydrophilic volatile PFAS can occur after prolonged extraction times (35 min +). Under these conditions, extended exposure allows higher-affinity analytes to displace more weakly retained species from the extraction phase. These results underscore the need for a balanced, data-driven approach to extraction time selection when targeting chemically diverse analytes, where extraction time is chosen to accommodate multiple compounds while minimizing competitive displacement, rather than defaulting to longer extraction times. Additionally, the selection of sorbents not susceptible to this effect (e.g., polyacrylate) is an important consideration for minimizing its occurrence.

Question 5. SPME is often cited as a cornerstone of Green Analytical Chemistry because it integrates sampling and extraction without solvents. As we look toward the future of environmental analysis, where do you see the role of microextraction technologies evolving? Do you think we will see tools like SPME Arrows replacing standard solvent extractions in regulatory workflows?

As environmental monitoring increasingly emphasizes sustainability alongside analytical performance, microextraction technologies are well aligned with Green Analytical Chemistry principles due to their minimal solvent use and reduced analytical footprint. Looking ahead, these techniques are likely to play an increasingly targeted role in environmental analysis, particularly as the field moves toward automatable, miniaturized workflows designed to address low sample volumes, complex matrices, and emerging contaminants. Tools such as SPME Arrows offer advantages in solvent reduction and automation, and their flexibility to operate in either direct immersion or headspace modes enhances compatibility with complex matrices, making them attractive alternatives to existing sample preparation regulatory workflows. Rather than broadly replacing solvent-based extractions, tools such as SPME Arrows are more likely to be integrated selectively into regulatory workflows for applications where their advantages are clearly demonstrated.

Question 7. Now that you have characterized these geometries for volatile PFAS, what is the next big question you are hoping to answer in your Ph.D. journey?

Having characterized how extraction geometry and agitation impact extraction efficiency for volatile PFAS, the next major question we are interested in is how SPME devices can perform across increasingly realistic and complex matrices. Specifically, I want to understand how matrix composition, coating phase chemistry, and physiochemical properties of neutral PFAS can influence partitioning, sampling, and preconcentration. Ultimately, the goal is to use the systematic insights gained from our comparison of SPME geometries to inform method design and interpretation when moving from controlled systems to real samples

Question 8. Finally, to wrap things up on a lighter note: A Ph.D. is a marathon, not a sprint. What are the top three items in your "Survival Kit" (music/playlists, specific snacks, hobbies, or lucky charms) that are currently powering you through the long days of instrument runs and data processing?

For long days of instrument runs and data processing, a few things have certainly become essential. The first is music, since each instrument seems to have its own personality, I ended up creating different playlists to match whichever one I’m working on that day, it’s a small but fun way to change things up. I even have a dedicated maintenance playlist for those days it’s time to vent and clean the GC source. The second is stepping away, usually a short walk helps reset my thinking and makes it easier to come back to data interpretation with fresh eyes. The third isn’t necessarily an item, but more of a perspective, unexpected results are a part of science and allowing myself to be curious about them rather than viewing them as something ‘bad’ has made a big difference in staying motivated, particularly for those projects where it feels like nothing goes as planned.

Further Reading & Resources

• Webinar: Automated PFAS Analysis with Madison Williams

• Application Note: Optimizing the Preconcentration of Volatile PFAS Precursors

• Original Paper: Williams, M. L., Cretnik, S., Lüthy, L., Flug, T., Stebler, M., & Gionfriddo, E. (2025). Comparison of solid phase microextraction geometries for effective preconcentration of volatile per- and polyfluoroalkyl substances. Analyst, 150, 1234-1245.