Development of Fluorinated SPME Sorbents for Selective PFAS Extraction and Chromatographic Analysis

Neutral volatile and semi-volatile PFAS, often called “forever chemicals,” are difficult to measure because they are usually present at extremely low levels and are mixed within complex environmental and consumer product samples. To address this challenge, a joint study conducted by Iowa State University and The State University of New York at Buffalo developed a new type of solid phase microextraction (SPME) material designed to selectively capture and concentrate fluorinated compounds before analysis.

The new SPME fibers were made using fluorinated polymeric ionic liquid (F-PIL) materials that contain both linear and branched fluorinated groups. Adding these fluorinated features improved the fibers’ ability to attract and retain PFAS compounds compared to non-fluorinated materials. The study also examined how the fibers interact with chemicals during extraction and found that some fibers behaved differently depending on their structure, with certain materials exhibiting stronger surface adsorption. Additional imaging studies revealed that fluorine-rich regions were unevenly distributed throughout the material, forming tightly clustered fluorinated domains that likely contributed to improved PFAS selectivity. The new fluorinated fibers were then compared with a commercial SPME fiber by testing their ability to extract volatile emissions from paint samples. The fluorinated PIL fibers showed much greater selectivity for PFAS and other fluorinated compounds, detecting these chemicals far more effectively than the commercial non-fluorinated fiber.

LCGC International spoke to the research team—Emanuela Gionfriddo and Madison Williams of the State University of New York at Buffalo, and Jared Anderson and SeongSoo Lee of Iowa State University—about their work, which has been featured recently in Analytical Chemistry.¹

How do fluorophilic interactions influence retention behavior in chromatographic systems when analyzing PFAS compared to traditional hydrophobic interactions?

Fluorophilic interactions describe intermolecular interactions between fluorocarbon groups driven by their unique characteristics such as hydrophobicity, high dipolarity, and low polarizability.² In our previous evaluation of fluorinated ionic liquid (IL) stationary phases for gas chromatography (GC), we observed that these fluorinated phases provided enhanced and selective retention of PFAS, particularly for compounds such as fluorotelomer alcohols and perfluoroalkenes.³ Enhanced retention and selectivity on fluorinated GC stationary phases were most pronounced for analytes with higher fluorine content, consistent with stronger fluorophilic interactions. In contrast, such improvements were not observed on non-fluorinated stationary phases. These findings highlight the critical role of fluorophilic interactions in achieving effective chromatographic separation of PFAS.

What characteristics of fluorinated polymeric ionic liquid (PIL) sorbents make them suitable as stationary phases or extraction coatings for selective PFAS analysis?

PILs consisting of repeating ionic liquid monomers have been used for developing diverse sample preparation methodologies due to their physicochemical characteristics including low volatility and high thermal stability. The primary benefit of PILs as sorbents is their excellent chemical and structural tunability. To develop sorbents enabling selective extractions of targeted analytes from samples, the components of PIL sorbents, including IL monomers and crosslinkers, can be carefully tailored by modifying their characteristics, such as polarity, hydrophobicity, aromaticity, and fluorophilicity. In this study, we found that PIL sorbents featuring fluorocarbon moieties were capable of selective extraction and preconcentration of volatile PFAS from the headspace of paint samples, which significantly reduced the coextraction of non-targeted volatile compounds compared to the commercial DVB/C-WR/PDMS fiber.¹

How does solid phase microextraction (SPME), particularly headspace SPME (HS-SPME), improve chromatographic analysis of volatile PFAS compared to direct injection methods?

SPME is a pre-concentration and extraction technique in which analytes are desorbed directly into the GC inlet without the use of solvent, enabling improved analyte focusing on the GC column under optimized conditions. The effect of pre-concentration and absence of co-solvent during desorption enables the achievement of lower limits of quantitation (LOQ) and detection (LOD). For HS-SPME, the extraction of non-volatile analytes is eliminated as sampling occurs exclusively from the HS of a sample. This reduction in matrix coextraction can directly enhance analyte signal and overall sensitivity in complex samples. It is important to note that HS-SPME is best suited for analytes with medium to high Henry’s law constants, which govern their ability to partition from the aqueous phase into the headspace. The volatile PFAS targeted in this study meet this criterion, supporting the suitability of the approach. Previous work from our group has demonstrated that when comparing the signal response for a sample spiked at 0.3 µg/L extracted using DI-SPME versus methanolic injection of the same standard at 300 µg/L, SPME resulted in an approximate 100-fold signal enhancement.⁴

Why do conventional sorbents like DVB/C-WR/PDMS lead to co-elution issues in PFAS analysis, and how can fluorinated PIL coatings mitigate these problems?

A key advantage of DVB/C-WR/PDMS extraction phases is the incorporation of two sorptive materials with complementary affinities. While carbon-wide range (C-WR) can extract small molecular weight (MW <150) volatile analytes, divinylbenzene (DVB) extracts larger volatile analytes and semi-volatile analytes, collectively enabling broad extraction coverage. Generally considered a strength of the DVB/C-WR/PDMS phase chemistry, the phase’s wide coverage can compromise selectivity for perfluorinated analytes, as non-specific affinities may promote competitive uptake from co-extracted non-fluorinated species. In contrast, fluorinated PIL sorbent phases mitigate these limitations by leveraging fluorophilic interactions, enabling selective extraction and pre-concentration of perfluorinated analytes, which in turn simplify chromatographic profiles, minimizing co-elution.

What chromatographic factors (for example, column efficiency, peak shape, or resolution) contribute to achieving low limits of quantitation (LOQs) for PFAS compounds?

Low LOQs for PFAS are achieved through optimization of chromatographic performance and stationary phase chemistry to maximize signal-to-noise (S/N). High column efficiency minimizes band broadening, producing narrow peaks with higher intensity. Good peak shape (symmetrical peaks) ensures accurate integration, while tailing reduces sensitivity. Adequate retention and resolution are essential to separate PFAS from matrix interferences and reduce background noise. The choice of stationary phase, particularly with fluorophilic interactions, further enhances selectivity.³ In GC×GC, modulation improves LOQs by refocusing analytes into narrow bands, increasing peak height and reducing co-elution. Proper modulation is critical, as poor settings can lead to undersampling or signal dilution. Overall, these factors work synergistically to enhance S/N and enable lower LOQs.⁵

How does an absorption-dominated extraction mechanism in PIL-based SPME fibers improve quantitative chromatographic analysis compared to adsorption-based mechanisms?

In absorption-type mechanisms, the analyte partitions into the whole volume of the sorbent coating within a reasonable extraction time and extraction amount is dependent on the coating volume. Whereas for adsorbent-type mechanisms, sorption only occurs on the active surface of the coating. Depending on the extraction time and affinity of the extracted analytes, this can lead to sorbent saturation and competitive adsorption as less-affine analytes are displaced by more-affine analytes, these effects however can be minimized by effective tuning and selection of extraction conditions. While, in general absorption-based phases can provide a broader linear dynamic range for quantification, adsorptive phases can display enhanced selectivity and sensitivity for specific analyte classes, depending on the phase chemistry.

What chromatographic strategies can be employed to minimize matrix effects and interferences when analyzing PFAS in complex environmental or biological samples?

There is no single chromatographic adjustment that eliminates matrix effects in PFAS analysis; rather, mitigation depends on combining chromatographic strategies and effective sample preparation. One such strategy is optimizing stationary phase chemistry: on conventional nonpolar phases (e.g., 5%-phenyl-methylpolysiloxane), separation is based on boiling point, potentially leading to co-elution of PFAS with hydrocarbons and background contaminants. Using more polar or fluorinated phases can better differentiate PFAS from matrix constituents, leading to elution in less congested regions of the chromatogram and improving signal-to-noise. Another approach is orthogonal multidimensional separation, such as comprehensive two-dimensional GC (GC×GC).⁵ By separating analytes across two independent mechanisms (volatility in the first dimension and polarity in the second), GC×GC can significantly increase peak capacity and redistribute matrix components across a two-dimensional space. Method development also plays a key role. Adjusting oven programs (GC) or mobile phase gradients (LC) can assist with the separation of highly abundant matrix compounds, potentially reducing baseline noise in critical elution windows. While these chromatographic strategies can reduce interferences, their effectiveness is ultimately constrained by the complexity of matrix introduced into the system. As such, the choice of sample preparation and extraction strategy becomes critical. Solid phase microextraction (SPME), a solventless preconcentration technique that features a tunable sorbent phase, is particularly well-suited for this purpose. By tailoring sorbent chemistry (e.g., polarity, fluorophilicity, and specific functional group interactions), SPME devices can be designed to preferentially extract PFAS while limiting the co-extraction of non-fluorinated matrix components.⁴ Together, the integration of selective chromatographic separation with tailored sample preparation techniques enables more effective control of matrix effects, ultimately improving the accuracy, sensitivity, and robustness of PFAS analysis in complex samples.

How can chromatographic comparison between fluorinated and non-fluorinated analogs help elucidate the dominant interaction mechanisms in PFAS extraction and separation?

The dominant interactions for chromatographic separations and selective extraction can be systematically evaluated by comparing results of fluorinated analytes to those of non-fluorinated analogs as control groups.^1,3 For example, the influence of fluorophilic interactions on chromatographic separation was elucidated by comparing the retention time and selectivity for 1-octanol and 6:2 fluorotelomer alcohol (FTOH) using fluorinated and non-fluorinated GC stationary phases. Moreover, the contribution of fluorophilic interactions for the selective extraction of volatile PFAS was investigated by evaluating the extraction efficiency of 1-octanol and 6:2 FTOH using non-fluorinated and fluorinated PIL fiber coatings.

References

1. Lee, S. S.; Williams, M. L.; Anderson, J. L. et al. Fluorinated Polymeric Ionic Liquids Enable Selective Preconcentration of Volatile Perfluoroalkyl Substances. Anal Chem. 2026 Apr 14;98(14):10693-10702. DOI: 10.1021/acs.analchem.5c08194
2. Román Santiago, A.; Yin, S.; Elbert, J. et al. Imparting Selective Fluorophilic Interactions in Redox Copolymers for the Electrochemically Mediated Capture of Short-Chain Perfluoroalkyl Substances. J. Am. Chem. Soc. 2023, 145 (17), 9508-9519. DOI: 10.1021/jacs.2c10963.
3. Ryoo, D.; Lee, S.-S.; Gionfriddo, E.; Anderson, J. L. Fluorinated Ionic Liquids as Gas Chromatographic Stationary Phases for the Separation of Volatile Per- and Polyfluoroalkyl Substances. Anal Chim Acta 2026, 1402, 345373. DOI: 10.1016/j.aca.2026.345373.
4. Martínez-Pérez-Cejuela, H.; Williams, M. L.; McLeod, C. et al. Effective Preconcentration of Volatile Per- and Polyfluoroalkyl Substances from Gas and Aqueous Phase via Solid Phase Microextraction. Anal Chim Acta 2025, 1345, 343746. DOI: 10.1016/j.aca.2025.343746.
5. Williams, M. L.; Fitzgerald, A.; Alonso, D. et al. Comparison of Solid Phase Microextraction Coatings for Headspace Extraction of Volatile Perfluoroalkyl Substances Using One-Dimensional and Comprehensive Two-Dimensional Gas Chromatography. Anal Chim Acta 2026, 1403, 345389. DOI: 10.1016/j.aca.2026.345389