Quantitative Analysis for Over 100 Native and Isotopically Labelled PFAS Compounds in Drinking and Surface Water by Triple Quadrupole LC/MS

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are persistent chemicals used in numerous industrial and consumer applications. Their environmental stability and potential health impacts have driven regulatory agencies to expand target lists and tighten monitoring requirements. Reliable, high-throughput analytical methods capable of quantifying a broad spectrum of native and isotopically labeled PFAS at trace levels in water matrices are essential for environmental monitoring, regulatory compliance, and risk assessment.

Study Objectives and Overview

This work describes the development of a comprehensive workflow combining solid phase extraction and triple quadrupole LC/MS/MS to quantify over 100 native and isotopically labeled PFAS compounds in drinking and surface water. The method leverages an Agilent PFAS MRM database to streamline acquisition setup and ensures broad analyte coverage while meeting stringent performance criteria.

Methodology and Extraction Workflow

Water samples (250 mL) were acidified to pH ≈ 3, spiked with isotopic surrogates and native PFAS at low and high levels, and loaded onto Agilent SampliQ Weak Anion Exchange (WAX) cartridges. After conditioning and loading steps, analytes were eluted and concentrated approximately 250-fold. Key steps include:

• Sample acidification and surrogate addition
• SPE cleanup using WAX cartridges on a Vac Elut manifold
• Elution, concentration, and reconstitution in 80:20 methanol:water

Instrumentation

Chromatographic separation was performed on an Agilent 1290 Infinity II UHPLC equipped with a PFC-Free HPLC Conversion Kit and a ZORBAX RRHD Eclipse Plus C18 column (2.1 × 100 mm, 1.8 µm). A 12-minute gradient of 5 mM ammonium acetate in water (A) and methanol (B) at 0.4 mL/min yielded an 18-minute injection-to-injection cycle.
Detection employed an Agilent 6470 triple quadrupole mass spectrometer with Jet Stream ESI in negative mode using dynamic MRM. The acquisition method was generated directly from the PFAS MRM database.

Key Results and Discussion

Calibration for 71 native PFAS used linear regression forced through zero with 1/x weighting (quadratic for FTSAs), achieving r2 > 0.99 across 3–4 orders of magnitude. Method detection limits for 60 PFAS ranged from 0.14 to 14 ng/L. The PFC-Free kit effectively eliminated background contamination; no PFAS peaks were observed in instrument or solvent blanks, and laboratory reagent blanks showed only trace levels below MDLs.
Precision and accuracy were robust: intra-batch RSD ≤ 20% and recoveries 71–129%; interbatch RSD 1.6–19.9% and recoveries 72–120%. A 93-hour sequence of 300 injections of high-level spikes demonstrated response ratio RSD ≤ 3.1% and RT RSD ≤ 0.10%, confirming sustained performance.

Benefits and Practical Applications

This method meets EPA quality criteria and supports high-throughput monitoring of drinking and surface water for a wide array of PFAS. It is suitable for environmental laboratories, QA/QC in industrial settings, and regulatory compliance programs. The approach is provided as an eMethod (G5285AA) for rapid implementation.

Future Trends and Potential Applications

Advances may include the integration of high-resolution MS for suspect and non-target screening, automation of SPE workflows, development of green extraction materials and solvents, miniaturized or field-deployable platforms, and application of machine learning for data interpretation and source apportionment.

Conclusion

A robust, sensitive LC/MS/MS method has been established for quantifying over 100 PFAS in water matrices. Utilizing SPE cleanup, a PFC-free UHPLC system, and dynamic MRM on a triple quadrupole, the workflow delivers excellent linearity, low detection limits, and long-term stability, addressing current and emerging analytical needs.

References

• Coggan LC, et al. A single analytical method for the determination of 53 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in aqueous matrices. Anal Bioanal Chem. 2019;411(16).
• US EPA. Definition and Procedure for the Determination of the Method Detection Limit, Revision 2. EPA 821-R-16-006. December 2016.