Routine EPA 1633 PFAS Analysis with a Novel Slotted Bandpass Ion Guide to Improve Signal Response Robustness

Significance of the Topic

The widespread presence of per- and polyfluoroalkyl substances (PFAS) in environmental and solid matrices poses critical challenges due to their persistence, toxicity, and regulatory scrutiny. Reliable quantitation of PFAS at trace levels is essential for compliance with EPA Method 1633A and to ensure accurate risk assessment and remediation strategies.

Objectives and Study Overview

This study aims to assess the integration of a novel slotted bandpass StepWave XR Ion Guide within the Xevo TQ Absolute XR tandem quadrupole mass spectrometer to enhance signal robustness in routine EPA 1633 PFAS analysis. The research evaluates long-term performance over more than 9 000 consecutive injections across diverse matrices, including river water, biosolids, and landfill leachate.

Methodology and Instrumentation

Sample Preparation:

• River water (250 mL) collected from River Tay, spiked with native and internal PFAS standards.
• Biosolid (0.5 g NIST 2781) and landfill leachate (25 mL LGC 6177) extracted and diluted 1 in 10 with methanol.

Analytical Conditions:

• Solid-phase extraction clean-up following EPA 1633A protocols.
• UPLC separation on ACQUITY Premier BEH C18 and Atlantis Premier BEH C18 AX columns, 2 mM ammonium acetate gradient.
• Detection with Xevo TQ Absolute XR MS in negative ESI mode, multiple reaction monitoring.
• StepWave XR Ion Guide installed to filter low-m/z noise and stabilise ion transmission.
• Data acquisition and batch review using waters_connect Quantitation Software.

Results and Discussion

Quality Control Performance:

• Weekly calibrations maintained linearity (1/x weighted) with ± 30 % trueness tolerance.
• Over 9 000 injections and 12 weeks, PFAS trueness ranged 70–130 % with %RSD below 8.8 % for key analytes (GenX, L-PFHxS, L-PFOS, PFBS, PFNA, PFOA).
• Biosolid extracts showed a mean PFOA value of 8.78 µg/kg (7.2 % RSD) close to the certified 9.39 µg/kg.
• Landfill leachate PFOA at 2.52 ng/mL with 2.7 % RSD demonstrated excellent reproducibility.

The StepWave XR Ion Guide significantly reduced background noise and prevented signal drift, enabling maintenance of system uptime without unscheduled downtime, aside from a single power cut.

Benefits and Practical Applications

• Enhanced method robustness via stable ion transmission across extended sequences.
• Reduced maintenance frequency and minimized instrument contamination.
• Reliable quantitation in aqueous, solid, and sludge matrices compliant with EPA 1633A.
• Accelerated data validation with seamless batch review in waters_connect.

Future Trends and Opportunities

Upcoming developments may include broader PFAS compound panels, integration of real-time diagnostics and AI-driven maintenance alerts, further improvements in ion guide design for ultra-trace analysis, and expansion into emerging matrices such as biota and food.

Conclusion

Incorporating the StepWave XR slotted bandpass ion guide into the Xevo TQ Absolute XR platform delivers robust, high-throughput PFAS analysis aligned with EPA 1633A requirements. The approach provides consistent sensitivity and long-term reliability, streamlining regulatory compliance and environmental monitoring workflows.

References

1. US Environmental Protection Agency. EPA Method 1633A: Analysis of Per- and Polyfluoroalkyl Substances in Aqueous, Solid, Biosolids, and Tissue Samples by LC-MS/MS; Dec 2024.
2. Organtini KL, Rosnack KJ, Plummer C, Hancock PM, Burt O. Analysis of Per- and Polyfluoroalkyl Substances in Accordance with EPA 1633 Part 2: Analysis of Aqueous Matrices. Waters Application Note 720008143; Dec 2023.
3. Organtini KL, Rosnack KJ, Plummer C, Hancock PM, Burt O. Analysis of Per- and Polyfluoroalkyl Substances in Accordance with EPA 1633 Part 3: Analysis of Soil and Tissue Samples. Waters Application Note 720008230; Feb 2024.