Determination of Per and Polyfluoroalkyl Substances in Soils Using Carbon S SPE by LC/MS/MS

Significance of the Topic

The persistence and mobility of per- and polyfluoroalkyl substances (PFAS) in soil environments pose significant challenges for environmental monitoring, risk assessment, and remediation strategies. Reliable analytical workflows are essential to detect trace-level PFAS in complex soil matrices, ensure regulatory compliance, and guide remediation efforts.

Objectives and Overview of the Study

This study describes the development and evaluation of a comprehensive method for simultaneous quantitation of 59 PFAS in diverse soil types. The approach combines a basic methanol extraction with a streamlined passthrough cleanup using Agilent Bond Elut Carbon S solid phase extraction (SPE) cartridges, followed by targeted analysis on an LC/MS/MS platform.

Methodology

The protocol was applied to three representative soil matrices: clean loamy sand, organic-rich reed sedge peat, and mixed agricultural topsoil. Two spike levels (0.625 and 6.25 ng/g) were used to assess recovery and precision. A 1% ammonia–methanol solvent extracted PFAS from 2 g of soil; extracts were neutralized, then passed through Carbon S cartridges to remove pigments and co-extractives. Isotope dilution quantitation employed 13C- and deuterated analogues. Calibration curves over 0.25–2.5 ng/mL used 1/x weighted linear regression including the origin.

Instrumentation

• Agilent 1290 Infinity II LC system with PFC-free HPLC conversion kit
• Agilent 6470B triple quadrupole MS with Jet Stream ESI source
• Agilent Bond Elut Carbon S SPE cartridges (250 mg, 6 mL)

Main Results and Discussion

Calibration accuracy for levels 2–6 ranged from 70% to 130% with an average near 95%. A separate 2 ng/mL QC check yielded 75–100% accuracy. Cartridge and blank extracts remained below reporting limits, confirming minimal PFAS background. Low-level recoveries averaged 99.3% (RSD 13.5%); high-level recoveries averaged 99.2% (RSD 8.5%). Carbon S cleanup visibly removed pigments in peat and topsoil. In reed sedge peat extracts, cleanup dramatically improved chromatographic peak shape and retention reproducibility for early-eluting PFBA. Environmental peat contained measurable PFBA (4.5 ng/g), PFPeA (2.98 ng/g), and PFHpA (0.83 ng/g); topsoil levels were below detection.

Benefits and Practical Applications

The method delivers high recovery and precision for a broad PFAS suite across varied soils, while reducing matrix interferences and system contamination. Its streamlined SPE passthrough cleanup facilitates high throughput, making it well suited for routine environmental monitoring, remediation verification, and compliance testing.

Future Trends and Applications

• Expansion of PFAS target lists to include emerging and ultra-short chain compounds
• Integration of high-resolution mass spectrometry for non-target screening
• Automation of sample preparation and SPE to increase laboratory throughput
• Development of standardized protocols for soil–water partitioning and bioavailability
• Coupling PFAS data with risk assessment models to guide site management

Conclusion

The Carbon S SPE–LC/MS/MS workflow offers robust, sensitive, and precise quantitation of 59 PFAS in soils. Efficient matrix removal, low background, and consistent performance across soil types support its adoption for environmental laboratories focused on PFAS analysis.

References

1. Weil RR, Brady NC. The Nature and Properties of Soils. 15th Ed. Pearson; 2017.
2. Zhao L, Wei T. Determination of Multiclass Pesticides in Spring Leaf Mix by Captiva EMR–HCF Cleanup and LC/MS/MS. Agilent Technologies Application Note 5994-4765EN; 2022.
3. Giardina M. Analysis of Per‐ and Polyfluoroalkyl Substances in Soil Extracts. Agilent Technologies Application Note 5994-2999EN; 2021.
4. Giardina M, Sun NL. Analysis of PFAS in Drinking Water Using SampliQ WAX SPE Cartridge. Agilent Technologies Application Note 5994-3616EN; 2021.
5. United States Environmental Protection Agency. Method 533: Determination of PFAS in Drinking Water by Isotope Dilution Anion Exchange SPE and LC-MS/MS. EPA; 2019.