Approaches to Non-targeted Analyses of Per- and Polyfluoroalkyl Substances (PFAS) in Environmental Samples

Importance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are highly stable synthetic compounds widely used in industry and consumer goods. Their persistence and bioaccumulative potential pose significant environmental and health concerns. Traditional targeted analyses often overlook novel or emerging PFAS, creating a need for comprehensive, non-targeted workflows to map the full extent of contamination.

Objectives and Study Overview

This study demonstrates non-targeted analysis workflows for PFAS determination in wastewater and soil extracts. By coupling ultra-performance liquid chromatography (UPLC) with high-resolution time-of-flight mass spectrometry (HR-TOF-MS) and leveraging custom reference libraries within the UNIFI platform, the approach aims to:

• Identify a broad range of legacy and emerging PFAS without prior selection.
• Assign putative structures using accurate mass, isotope patterns, fragmentation, and retention time.
• Discover unidentified PFAS via database searching and structural elucidation tools.

Methodology and Instrumentation

Samples were prepared following ASTM protocols and spiked with isotope-labeled internal standards. The PFAS-free UPLC system was fitted with a dedicated isolator column to reduce background. Key operating conditions:

• Chromatography: ACQUITY UPLC I-Class PLUS with PFAS kit, C18 column, 0.3 mL/min, gradient of water/methanol (2 mM ammonium acetate).
• Detection: Xevo G2-XS QTof MS in negative ESI, full scan (50–1200 Da), MSE data-independent acquisition.
• Data processing: UNIFI v1.9.4 with in-house libraries (>4,200 entries), ChemSpider integration.

Key Results and Discussion

The non-targeted workflow successfully detected and assigned all 30 PFAS spiked into wastewater (mass errors ≤1.1 mDa). Customizable filters (retention time window, mass defect, fragment matching) streamlined data review. In soil extracts, perfluoroether sulfonic acid derivatives were identified and confirmed by targeted MS/MS, with quantitation demonstrating concentrations down to single-digit ng/g levels. Structural elucidation tools (common fragment, neutral loss, mass defect searching) enabled discovery of novel PFAS not present in the library, later confirmed via database matching and authentic standards.

Benefits and Practical Applications of the Method

The described technique offers:

• Simplified sample preparation minimizing analyte loss.
• Comprehensive coverage of known and unknown PFAS classes.
• High confidence in assignments through multiple orthogonal attributes.
• Discovery capability for novel PFAS, aiding environmental forensics and remediation.

Future Trends and Opportunities

Advancements may include expansion of spectral and chromatographic databases, integration of machine learning algorithms for pattern recognition, broader application to diverse environmental and biological matrices, and real-time data mining during acquisition. Collaboration with regulatory bodies to standardize non-targeted PFAS screening workflows will further support risk assessment and pollution control.

Conclusion

Non-targeted UPLC-HR-TOF-MS workflows powered by custom PFAS libraries and the UNIFI platform enable comprehensive profiling of both legacy and emerging PFAS in environmental samples. This methodology delivers increased confidence in compound identification, facilitates discovery of unknown contaminants, and provides a versatile tool for environmental monitoring and source apportionment.

Instrumentation Used

• ACQUITY UPLC I-Class PLUS System with PFAS Analysis Kit
• Xevo G2-XS QTof Mass Spectrometer (ESI Negative, MSE Acquisition)
• UNIFI Scientific Information System v1.9.4

References

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