Determination of 40 PFAS in Biosolids Following EPA Method 1633 Quality Control Guidance

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants of growing concern due to their toxicity and resistance to degradation. Biosolids, derived from treated sewage sludge, can concentrate PFAS and serve as a pathway for land application and human exposure. Reliable analysis of PFAS in biosolids is essential for environmental monitoring, regulatory compliance, and risk assessment.

Objectives and Study Overview

This work aimed to develop and validate a rapid, high-throughput method for simultaneous quantitation of 40 PFAS in biosolid matrices following EPA Method 1633 quality control guidance. Key objectives were:

• Integrate a streamlined QuEChERS extraction with enhanced matrix removal (EMR) cleanup using Agilent Captiva EMR PFAS Food II cartridges.
• Implement sensitive LC/MS/MS detection with isotope dilution quantitation.
• Demonstrate method performance—accuracy, precision, limits of detection and quantitation—according to EPA 1633 criteria.

Methodology and Instrumentation

Použitá instrumentace

• Agilent 1290 Infinity II LC system with PFC-free conversion kit and delay column.
• Agilent 6495D triple quadrupole LC/MS with JetStream iFunnel electrospray source.
• Captiva EMR PFAS Food II cartridges (6 mL, 750 mg).
• Bond Elut QuEChERS EN extraction kits.
• NIST SRM 2781 Domestic Sludge for reference and QC.

Sample preparation combined QuEChERS salt extraction in 10 mL acetonitrile with 1% acetic acid and 0.5 g biosolid, followed by EMR mixed-mode passthrough cleanup. Isotopically labeled internal standards (24 EIS and 7 NIS) were used to correct recoveries and matrix effects. LC separation employed ZORBAX RRHD Eclipse Plus C18 columns, and quantitation was based on neat standard calibration (1/x2 weighting) over dynamic ranges tailored to individual PFAS concentrations.

Main Results and Discussion

Method performance in biosolids demonstrated:

• Method detection limits (MDLs) from 0.01 to 16 µg/kg and LOQs from 0.03 to 136 µg/kg, generally below EPA-estimated values for biosolids.
• Average recoveries for PFAS targets within 70–120% acceptance, RSDs under 15% at low and mid spike levels for most analytes.
• EIS and NIS recoveries within EPA 1633 criteria, confirming effective matrix removal; RSDs for internal standards under 10%.
• Proficiency testing on NIST 2781 showed concentrations for PFHxA, PFHpA, PFOA, PFOS within certified ranges and RSDs below 5%, outperforming previous methods.

Benefits and Practical Applications

The QuEChERS-EMR workflow halves sample preparation time and reduces solvent and consumable use by over 50% compared to conventional SPE-based EPA 1633 methods. It delivers robust quantitation with streamlined operations suitable for high sample throughput in environmental monitoring, wastewater treatment profiling, and regulatory laboratories.

Future Trends and Possibilities

Advances may include:

• Extension of EMR cleanup to other complex matrices such as soil, compost, and biosolid amendments.
• Integration with high-resolution accurate mass spectrometry for non-targeted PFAS screening.
• Automation of QuEChERS-EMR steps for further throughput gains.
• Development of miniaturized extraction formats to lower sample and solvent requirements.

Conclusion

This study presents a validated, efficient, and cost-effective method for quantifying 40 PFAS in biosolids, fully compliant with EPA Method 1633 guidance. The method’s combination of QuEChERS extraction and EMR cleanup ensures reliable matrix removal and accurate isotope dilution LC/MS/MS analysis, making it a robust alternative to traditional SPE workflows for environmental PFAS monitoring.

References

1. U.S. Environmental Protection Agency. Method 1633, Revision A: Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS; EPA 820-R-24-007, 2024.
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10. National Institute of Standards and Technology. SRM® 2781 Domestic Sludge, Certificate of Analysis, 2024.
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