Improved Sensitivity for the Detection of Per- and Polyfluorinated Alkyl Substances in Environmental Water Samples Using a Direct Injection Approach on Xevo™ TQ Absolute

Importance of the Topic

The analysis of per- and polyfluorinated alkyl substances (PFAS) in water is increasingly critical as global regulations tighten limits to protect human health and the environment. Reliable and sensitive detection methods enable water testing laboratories to meet stringent requirements, ensure compliance, and safeguard public water supplies.

Objectives and Study Overview

This study evaluates a streamlined direct injection approach for PFAS analysis in environmental water samples using reduced injection volumes on the Xevo TQ Absolute tandem quadrupole mass spectrometer. Four representative matrices—drinking water, groundwater, surface water, and influent wastewater—were assessed to determine method detection limits (MDLs), sensitivity, precision, and applicability across diverse sample types.

Methodology

Samples were prepared via a simple dilute-and-shoot protocol. Following EPA guidelines (821-R-16-006), replicate spikes in reagent water established MDLs for 33 PFAS compounds, covering carboxylates, sulfonates, known precursors, and emerging analytes. Chromatographic separation employed a binary gradient of 2 mM ammonium acetate in water and methanol. Mass spectrometric acquisition used optimized negative ion transitions and collision energies.

Used Instrumentation

• UPLC: ACQUITY UPLC I-Class PLUS System FTN with PFAS Analysis Kit
• Mass Spectrometer: Xevo TQ Absolute Tandem Quadrupole MS
• Software: MS Quan application within waters_connect for quantitative processing

Key Results and Discussion

MDLs for the 10 µL direct injection ranged from 0.8 to 2.0 ng/L, with slightly elevated values for PFBA, PFPeA, and 6:2 FTS due to background contamination. Calibration curves exhibited linearity from 0.5 to 250 ng/L and met typical EPA deviation criteria (±50% at LLOQ, ±30% elsewhere). Chromatograms of PFOS isomers spiked into wastewater demonstrated detection of both branched and linear forms at sub-ng/L levels. Repeat injections of a 10 ng/L control sample (n=7) delivered precision better than 10% RSD for all compounds. Four real water sample matrices yielded confident quantitation of most PFAS below 5 ng/L using the reduced-volume method.

Benefits and Practical Applications

• Minimal sample preparation accelerates throughput and reduces contamination risk.
• Small injection volume enhances column longevity and source cleanliness.
• High negative-ion sensitivity facilitates low-level PFAS quantitation without solid-phase extraction.

Future Trends and Opportunities

Advances in mass spectrometer sensitivity will further expand direct injection capabilities for trace-level contaminants. Integration with automated sample handling and real-time data analytics may streamline PFAS monitoring across regulatory and research laboratories. Emerging PFAS structures will require ongoing method adaptation and validation.

Conclusion

The Xevo TQ Absolute permits robust direct injection analysis of PFAS in diverse water matrices with injection volumes as low as 10 µL, achieving MDLs of 0.8–2.0 ng/L. This approach offers a rapid, high-throughput option that maintains analytical performance while reducing maintenance and consumable use.

References

1. Organtini K, Cleland G, Rosnack K. Large Volume Direct Injection Method for the Analysis of Perfluorinated Alkyl Substances in Environmental Water Samples. Waters Application Note 720006329, 2018.
2. Willmer H, Organtini K, Adams S. Routine Determination of PFAS in Drinking Water by Direct Injection Using UPLC-MS/MS to Meet EU Directive 2020/2184. Waters Application Note 720007413, 2021.
3. US EPA. Definition and Procedure for the Determination of the Method Detection Limit, Revision 2. EPA 821-R-16-006, 2016.