LEGACY AND EMERGING PERFLUORINATED ALKYL SUBSTANCES (PFAS) IN WATER: DEVELOPING AN SPE METHOD FOR LC-MS/MS ANALYSIS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants with widespread use in industrial and consumer products. Their chemical stability and resistance to degradation have led to global dissemination in water resources, posing risks to ecosystems and human health. Sensitive analytical methods are essential to reliably detect both legacy compounds (e.g., PFOA, PFOS) and emerging PFAS at sub-ppt levels.

Aims and Study Overview

This study aimed to develop and validate a solid-phase extraction (SPE) sample preparation method coupled with LC-MS/MS for the simultaneous analysis of 40 legacy and emerging PFAS in various environmental water matrices. Performance was evaluated in surface water, groundwater, influent wastewater, and final effluent samples.

Methodology

Sample Collection and Preparation:

• Water types: surface, groundwater, influent and final effluent wastewater.
• Sampling containers: 250 mL HDPE bottles; samples acidified to pH < 3 and filtered.
• SPE enrichment: Oasis WAX 6 cc/150 mg cartridges conditioned with ammonia/methanol, methanol, and water; water samples loaded, rinsed, and eluted to yield a 250× concentration factor.

Used Instrumentation

• LC System: ACQUITY UPLC I-Class Plus with PFC kit.
• Column: ACQUITY UPLC BEH C18, 2.1 × 100 mm, 1.7 μm; column temperature 35 °C; sample temperature 10 °C.
• Mobile Phase A: 95:5 water:methanol with 2 mM ammonium acetate; Phase B: methanol with 2 mM ammonium acetate; gradient elution over 22 min.
• MS System: Xevo TQ-S micro; ESI negative mode; capillary voltage 0.5 kV; desolvation 350 °C at 900 L/h; cone gas 100 L/h; source 100 °C; MRM transitions optimized in MassLynx.

Main Results and Discussion

• Recoveries: Most PFAS showed recoveries between 75 % and 130 % after isotope-standard correction; PFBA and 6:2 FTS exhibited higher recoveries due to background contamination.
• Reproducibility: Six replicates of spiked groundwater yielded RSDs < 15 % for all analytes (majority < 10 %).
• Limits of Detection: In-vial LODs ranged from < 2 ng/L to 500 ng/L, corresponding to sample LODs of < 0.01 ng/L to 2 ng/L, with linearity (R²) ≥ 0.988.
• Method Robustness: Twenty replicate injections of spiked surface water showed < 10 % RSD in peak area, stable retention times, and consistent ion ratios for PFOA and other PFAS.
• Environmental Survey: Distinct PFAS profiles and concentration patterns were observed across water types; legacy compounds dominated in wastewater influent, while emerging PFAS appeared in surface and groundwaters.

Benefits and Practical Applications

• The SPE-LC-MS/MS workflow achieves high enrichment (250×) enabling sub-ppt detection aligned with US EPA and EU regulatory guidelines.
• Robust recoveries and reproducibility support routine monitoring in laboratories focused on QA/QC, environmental research, and industrial compliance.
• Adaptability to diverse water matrices allows comprehensive screening of legacy and novel PFAS in environmental surveillance programs.

Future Trends and Potential Applications

• Integration of automated SPE platforms to increase sample throughput and consistency.
• Expansion to high-resolution MS for non-target screening of novel PFAS and transformation products.
• Application of the method to additional matrices such as biota, soil, and wastewater treatment solids.
• Development of standardized multi-organization protocols for interlaboratory comparability and regulatory harmonization.

Conclusion

The presented SPE enrichment and LC-MS/MS method provides a sensitive, precise, and reproducible approach for quantifying a broad spectrum of PFAS in environmental water samples. Recoveries, detection limits, and robustness meet stringent advisory levels, supporting its implementation in environmental monitoring and regulatory compliance.

References

• Organtini K., Rosnack K., Stevens D., Ross E., Lai S. Legacy and Emerging Perfluorinated Alkyl Substances (PFAS) in Water: Developing an SPE Method for LC-MS/MS Analysis. Waters Application Note 720006471EN, 2019.
• ISO 25101:2009. Water Quality—Determination of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) Using Solid-Phase Extraction and LC-MS.
• US EPA. Drinking Water Health Advisory for PFOA and PFOS, 2016.
• European Commission. Water Framework Directive and Drinking Water Directive PFAS Standards.