LC/MS/MS Determination of PFOS and PFOA in Water and Soil Matrices

Significance of the Topic

PFOS and PFOA are persistent perfluorinated chemicals with known health and environmental risks, including potential carcinogenic and developmental effects. Sensitive and reliable analytical methods are essential for environmental monitoring, risk assessment, and regulatory compliance.

Objectives and Overview of the Study

This application note describes the development and validation of an LC/MS/MS method using an Agilent 1290 Infinity II LC coupled with an Ultivo triple quadrupole mass spectrometer to determine trace levels of PFOS and PFOA in various water and soil matrices. The study aimed to achieve sub-ng/L detection in water and ng/kg detection in soil, with high accuracy, precision, and throughput across diverse sample types.

Methodology

Sample Preparation:

• Water samples (500 mL) were filtered and spiked with 13C4-labelled internal standards.
• Soil and sediment (5 g) were extracted with methanol, vortexed or shaken, centrifuged, and diluted to reduce methanol content below 10%.
• Cleanup used weak anion exchange (WAX) SPE cartridges: cartridges were conditioned, samples loaded at pH 4.0, washed with buffer and methanol, dried, and eluted with ammonia/methanol.
• Eluates were evaporated under nitrogen at 40 °C and reconstituted in methanol for analysis.

Instrumentation Used

Liquid Chromatography:

• Agilent 1290 Infinity II LC with built-in degasser and temperature-controlled autosampler.
• Agilent InfinityLab Poroshell 120 EC-C18 column (2.1×100 mm, 2.7 µm) at 35 °C.
• Binary gradient: water with 2 mmol/L ammonium acetate (A) and acetonitrile (B) over a 5 min runtime.

Mass Spectrometry:

• Agilent Ultivo triple quadrupole MS in negative ion mode.
• Optimized MRM transitions: PFOA 413→369 (quantifier), PFOS 499→99 (quantifier); corresponding transitions for 13C4 analogs.
• Controlled drying gas, sheath gas, and collision energies to maximize sensitivity.

Main Results and Discussion

Calibration and Sensitivity:

• Excellent linearity from 0.5 to 200 µg/L (R²≥0.997) for both PFOS and PFOA.
• Limits of detection at sub-ng/L in water and low ng/kg in soil.

Accuracy and Precision:

• Spiking recoveries in pure water, river water, and wastewater ranged from 88.4 to 98.8% for PFOA and 88.0 to 97.3% for PFOS (RSD ≤14%).
• Recoveries in blank soil, field soil, and sediment ranged 96.8 to 113% (RSD ≤6.6%).

Real Sample Application:
Analysis of environmental samples indicated PFOS and PFOA at levels from single ng/L to tens of ng/L in water, with most soil and sediment samples below detection, confirming method robustness for routine monitoring.

Benefits and Practical Applications

The method delivers rapid analysis (5 min per run), low detection limits, high throughput, and robust cleanup for diverse matrices. It supports regulatory surveillance, pollution source identification, and environmental risk assessments.

Future Trends and Opportunities

• Integration of trapping columns or inline cleanup to extend column lifetime and reduce carryover.
• Adoption of greener solvents and miniaturized extraction techniques for sustainability.
• Expansion toward comprehensive PFAS panels including emerging analogs.
• Automated sample preparation and online SPE for increased throughput.
• Evolving regulatory guidelines driving method adaptation for new PFAS standards.

Conclusion

The Agilent 1290 Infinity II LC coupled with Ultivo TQ MS, combined with WAX SPE and isotopic dilution, provides a sensitive, accurate, and reproducible approach for quantifying PFOS and PFOA in environmental water and soil. Achieving sub-ng/L and ng/kg detection levels, the method meets stringent requirements for routine environmental monitoring.

References

1. Yang W. L. et al. China Journal of Environmental Chemistry (in press).
2. Loos R. et al. Chemosphere 2008, 71(2), 306–313.
3. Inoue K. et al. Environ. Health Perspect. 2004, 112(11), 1204–1207.
4. EFSA. Opinion on PFOS and PFOA in food, 2008.
5. US EPA. PFOA & PFOS Drinking Water Health Advisories, EPA 800-F-16-003, 2016.
6. Pan Y. Y. et al. Sci. China Chem. 2011, 54(3), 552–558.
7. Yu Y. et al. J. Agric. Food Chem. 2015, 63(16), 4087–4095.
8. Wang Y. X. et al. China J. Environ. Chem. 2018, 37(6), 1197.
9. GB 5009.253–2016. Method for determination of PFOS/PFOA in food of animal origin.