Waters Application Notes - Environmental

Significance of the topic

Environmental water matrices increasingly contain a wide range of emerging contaminants, including per- and polyfluoroalkyl substances (PFASs). These compounds are persistent, bioaccumulative, and have potential toxic effects even at part-per-trillion levels. Sensitive, selective, and high-throughput analytical methods are required to monitor both legacy PFASs (e.g., PFOA, PFOS) and newer replacement compounds (ADONA, 9Cl-PF3ONS, 11Cl-PF3OUdS) in diverse water matrices.

Study objectives and overview

This work applies the ASTM D7979-17 large volume direct injection protocol to monitor 39 PFAS compounds in environmental water samples. An ACQUITY UPLC I-Class System, fitted with a PFC Analysis Kit, and Xevo TQ-S micro tandem quadrupole MS were evaluated. The objectives were to confirm method detection limits (MDLs) below required reporting levels, assess method linearity, examine SPE enrichment performance, and demonstrate application to surface, ground, and waste water samples in compliance with regulatory guidance.

Methodology and instrumentation used

• Sample preparation followed ASTM 7979-17: 5 mL water samples spiked with 160 ng/L isotopically labeled surrogates, diluted with methanol, filtered, and acidified.
• Large volume injection: 10 µL directly injected on UPLC, achieving up to 1,000× enrichment.
• Chromatography: ACQUITY UPLC I-Class System with PFC Analysis Kit, CSH Phenyl Hexyl Column (2.1×100 mm, 1.7 µm), gradient 5–95% methanol in water (2 mM ammonium acetate) over 14 min.
• MS/MS detection: Xevo TQ-S micro, ESI- with optimized MRM transitions, cone voltages and collision energies via QuanOptimize.

Main results and discussion

• MDLs for 39 PFASs were all below method reporting limits (10–400 ng/L), with MDLs of 1–50 ng/L achieved for most compounds.
• Calibration curves were linear across method ranges (R² ≥ 0.98) and reproducible (compound recoveries 75–130%).
• SPE recoveries in reagent water, ground water, surface water, influent and effluent waste water were generally 75–130%, with RSDs < 10%.
• Matrix effects were observed in complex samples; additional wash steps or matrix-matched calibration can address ion suppression.
• Environmental application: up to 27 PFASs were detected in surface, ground, and waste water samples at ng/L levels, including emerging compounds ADONA and F-53B components.

Benefits and practical applications of the method

• Minimal sample preparation and direct injection significantly increase throughput for environmental PFAS monitoring.
• Large volume injection on Xevo TQ-S micro provides sensitive detection, ensuring compliance with EPA and EU reporting requirements.
• The PFC Analysis Kit ensures a PFAS-free LC system and robust chromatography, reducing background contamination.
• Method versatility allows screening of both legacy and emerging PFASs in diverse matrices without extensive cleanup.

Future trends and possible applications

• Expansion of target analyte lists to include newly identified PFASs as standards become available.
• Integration with high-resolution MS (e.g., Xevo G2-XS QTof) for untargeted screening of unknown PFASs and transformation products.
• Adoption of automation and 2D UPLC workflows for further increases in sample throughput.
• Combined use of direct injection and SPE methods to optimize sensitivity across compound classes.

Conclusion

The large volume direct injection method, coupled with the PFC Analysis Kit, effectively meets regulatory requirements for PFAS monitoring at low ng/L levels. The technique offers high sensitivity, reliable quantification, and robust performance across various environmental matrices, providing an efficient solution for legacy and emerging PFAS analysis.

References

1. Secretariat of the Stockholm Convention. Stockholm Convention POPs. https://chm.pops.int.
2. U.S. EPA UCMR3. https://www.epa.gov/dwucmr/third-unregulated-contaminant-monitoring-rule.
3. EPA PFOA & PFOS Drinking Water Health Advisories. https://www.epa.gov.
4. Directive 2013/39/EU. https://eur-lex.europa.eu/.
5. ASTM D7979-17. Determination of PFAS in water by LC-MS/MS. ASTM International, 2017.
6. Mullin L, Burgess J. Ultra low-level detection of PFASs using PFC Analysis Kit. Waters Tech Brief; 2016.