Development of Screening Analysis Method for Per- and poly-fluoroalkyl Substances (PFAS) in Surface Water on LC-Q-TOF

Significance of the Topic

Per- and polyfluoroalkyl substances (PFAS) are synthetic fluorinated compounds that persist in water, soil, food and living organisms. Due to their extreme stability and widespread use, PFAS pose significant environmental and health risks. Standard targeted methods monitor only a limited subset of PFAS, potentially underestimating their presence. Developing comprehensive screening approaches is therefore critical for accurate risk assessment and regulatory compliance.

Objectives and Study Overview

This study aimed to establish a high-resolution LC-Q-TOF method for simultaneous targeted and untargeted screening of known and unknown PFAS in surface and groundwater. The approach combines a curated library of 34 PFAS standards with a novel workflow leveraging mass defect filtering and diagnostic fragment ions to detect emerging PFAS candidates.

Methodology and Used Instrumentation

Liquid chromatography was performed on a Shim-pack GIST C18 column (100 mm × 2.1 mm, 2 μm) using a 45 min gradient from 10 % to 95 % acetonitrile in 5 mM NH₄OAc at 0.4 mL/min. Mass spectrometry was carried out on a Shimadzu LCMS-9030 Q-TOF with heated electrospray ionization in negative mode. Data-dependent acquisition (DDA) collected MS/MS spectra concurrently with full scan data. Key settings included argon CID at 270 kPa, interface temperature 400 °C, block 300 °C and drying gas flows of nitrogen and zero air.

Main Results and Discussion

The targeted library of 34 PFAS showed mass errors within 3 ppm and well-resolved retention times. In a river water sample (W26), PFOA and PFOS were identified with MS and MS/MS spectral matches above 90 % and mass errors below 0.2 ppm. Untargeted screening applied a mass defect window (–10 to –120 mDa) and searched for characteristic fragments (C2F5–, C3F7–, SO3–). This workflow revealed a novel PFAS candidate at m/z 382.9418, assigned as perfluorohexyl sulfinic acid (C6F13SO2H) based on exact mass, diagnostic ions and structural prediction.

Benefits and Practical Applications

The integrated targeted/untargeted strategy enhances environmental monitoring by covering regulated PFAS and uncovering unknown analogues. Laboratories can apply this workflow for routine water quality testing, environmental risk evaluation and discovery of emerging PFAS contaminants.

Future Trends and Potential Applications

Advances in high-resolution mass spectrometry, expanded suspect screening databases and AI-driven spectral interpretation will further improve PFAS identification. Future work will extend this approach to other environmental matrices, automate data processing and develop high-throughput screening for comprehensive PFAS surveillance.

Conclusion

A robust LC-Q-TOF method was developed for concurrent targeted and untargeted PFAS screening in water. It reliably identified known compounds and detected a novel sulfinic acid derivative, demonstrating the value of mass defect filtering and diagnostic fragments for non-target PFAS discovery.

Reference

• Shoemaker J; Tettenhorst D. EPA Method 537.1: Determination of Selected Per- and Polyfluorinated Alkyl Substances in Drinking Water by Solid Phase Extraction and LC-MS/MS. US EPA, 2018.
• EPA Researchers Use Innovative Approach to Find PFAS in the Environment. EPA Science Matters, April 2019.
• Liu Y et al. High-resolution mass spectrometry methods for non-target discovery and characterization of PFAS in environmental and human samples. Trends Anal Chem, 2019.