Methodologies for Ultrashort-Chain and Comprehensive PFAS Analysis in Water Samples

Importance of the Topic

Ultrashort‐chain per- and polyfluoroalkyl substances (PFAS) with carbon chains shorter than C4 are increasingly detected in environmental waters. Their high polarity and small size make them difficult to analyze using conventional reversed-phase liquid chromatography. Effective measurement of these compounds is critical for environmental monitoring, risk assessment, and emerging regulatory standards.

Study Objectives and Overview

This work presents two complementary liquid chromatography–tandem mass spectrometry (LC-MS/MS) workflows:

• A targeted method for C1–C4 PFAS using a hybrid HILIC/ion-exchange Polar X column and direct injection (Polar X Method).
• A comprehensive dilute-and-shoot method covering C1–C14 perfluoroalkyl carboxylic and sulfonic acids and related PFAS classes using an inert-coated polar-embedded alkyl phase Ultra Inert IBD column.

Both approaches were evaluated for linearity, accuracy, and precision in fortified drinking water and various wastewater effluents.

Methodology and Instrumentation

Sample preparation was simplified to direct injection or dilute-and-shoot. Drinking water and bottled water were fortified with isotopically labeled internal standards and injected directly. Wastewater samples were filtered prior to analysis. Calibration standards spanned low-ppt to low-ppb levels.

• Columns and Delay Line
  • Raptor Polar X 50 × 2.1 mm, 2.7 µm (C1–C4 PFAS)
  • Ultra Inert IBD 100 × 2.1 mm, 3 µm (C1–C14 PFAS)
  • PFAS Delay Column to minimize background contamination
• LC-MS/MS Conditions
  • Mobile phases: aqueous ammonium formate/formic acid and organic solvents with formic acid or acetic acid modifiers
  • Flow rates 0.3–0.4 mL/min, column temperature 40 °C, injection volumes 10–45 µL
  • Electrospray ionization in negative MRM mode

Key Results and Discussion

Linearity for both methods exceeded r² > 0.995 across the calibration ranges (1–1000 ng/L for comprehensive method; 2.5–800 ng/L for C1–C4).

• Accuracy and Precision
  • Polar X Method recoveries: 86.6–107% with RSD 1.6–10.7% across three water types and fortification levels.
  • Ultra Inert IBD Method recoveries: 70–130% with RSD < 20% for 45 targeted PFAS.
• Application to Real Samples
  • Measured ultrashort-chain PFAS (TFA, PFPrA, TFMS) at tens to hundreds of ng/L in tap, bottled, spring, well, and creek waters.
  • Wastewater effluents showed elevated PFAS levels, confirming method suitability for diverse matrices.

Benefits and Practical Applications

These workflows provide robust, high-throughput solutions for PFAS surveillance in environmental and drinking water laboratories. Minimal sample preparation reduces analysis time and contamination risk. The methods support quality assurance, regulatory compliance, and rapid response monitoring.

Future Trends and Potential Applications

Emerging directions include:

• Extension to non-aqueous matrices (soil, biota)
• Integration with high-resolution mass spectrometry for non-target screening
• Automation and online sample cleanup to further streamline workflows
• Adoption of standardized protocols for regulatory guidance

Conclusion

Two validated LC-MS/MS approaches enable accurate quantification of ultrashort and a broad range of PFAS in water samples. The demonstrated linearity, accuracy, and precision across environmental and potable water matrices make these methods valuable tools for routine monitoring and future regulatory efforts.