Application of a MRM Database for the Quantitation of Per and Polyfluoroalkyl Substances (PFAS) in Water Extracts

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent environmental contaminants widely used for their unique chemical properties in consumer products and industrial applications. Their environmental persistence and potential health risks have led to stringent regulatory requirements and the need for robust, high-throughput analytical methods to quantify a growing list of legacy and emerging PFAS in water matrices.

Objectives and Study Overview

This study aimed to develop and validate three multiple reaction monitoring (MRM) databases for the simultaneous quantitation of over 100 native and isotopically labelled PFAS compounds in water extracts. The databases were tailored for three Agilent triple quadrupole LC/MS systems—Ultivo LC/TQ, 6470B LC/TQ, and 6495C LC/TQ—to support diverse analytical laboratories and regulatory methods such as EPA 533 and 537.

Methodology and Instrumentation

Sample preparation followed EPA Method 537.1 for drinking water, surface water, and wastewater. Key steps included solid-phase extraction, drying, and reconstitution in 80:20 methanol:water. Post-spike recoveries were assessed at 2, 8, and 20 ng/mL.

MRM parameters (collision energy, fragmentor voltage) were optimized using Agilent MassHunter Optimizer. AJS source settings were tuned with the Source Optimizer tool. Calibration standards comprised twelve levels (0.01–100 ng/mL) of native PFAS with isotopically labelled analogues spiked at 5 or 40 ng/mL.

Instrumentation

• Agilent 1290 Infinity II UHPLC with PFC-Free HPLC Conversion Kit (part 5004-0006) to minimize background contamination.
• Columns: ZORBAX RRHD Eclipse Plus C18, 2.1 × 100 mm, 1.8 µm.
• Mass spectrometers: Ultivo LC/TQ, 6470B LC/TQ, 6495C LC/TQ operated in negative electrospray ionization mode.
• Injection volumes: 5 µL (Ultivo), 3 µL (6470B), 2 µL (6495C).

Main Results and Discussion

The curated MRM databases include compound identifiers, retention times, and optimized MRM transitions for 72 native and 36 labelled PFAS representing multiple chemical classes. Key performance metrics across the three platforms were:

• Linearity: All analytes exhibited R² > 0.99 (except one at R² = 0.98), over 3–4 orders of magnitude.
• Accuracy: 71–129% across calibration levels, meeting EPA criteria.
• Instrument Detection Limits (IDLs): Ranged from 2.3 to 9210 fg on-column, with most below 5000 fg.
• Precision: Retention time RSD ≤ 0.82%; area RSD ≤ 18% in drinking and surface water, slightly higher for a few compounds in wastewater.
• Recoveries: Post-spike recoveries averaged 90–93% across matrices.

Benefits and Practical Applications

The developed MRM databases enable rapid method development and expansion of analyte lists for targeted PFAS analysis. Laboratories can customize sub-methods based on regulatory or research needs, improving throughput and consistency for environmental monitoring, QA/QC, and regulatory compliance.

Future Trends and Prospects

Further enhancement is anticipated through integration with high-resolution mass spectrometry for non-target screening of novel PFAS, automation of sample preparation workflows, and global harmonization of analytical standards and regulatory guidelines. Advances in software-driven database management will support ongoing updates as new fluorochemicals emerge.

Conclusion

This study demonstrates a robust, reproducible MRM-based quantitation strategy for over 100 PFAS in water extracts using three Agilent LC/TQ systems. The comprehensive databases, combined with minimized background contamination and optimized parameters, offer a practical solution for labs facing evolving regulatory requirements and diverse PFAS challenges.

Reference

1. Coggan L.C., et al. A single analytical method for the determination of 53 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in aqueous matrices. Analytical and Bioanalytical Chemistry. 2019;411(16):411–427.
2. Gremmel C., et al. HPLC-MS/MS methods for the determination of 52 perfluoroalkyl and polyfluoroalkyl substances in aqueous samples. Analytical and Bioanalytical Chemistry. 2017;409(6):1643–1655.