PFAS analysis strategy story – direct injection, DLLME, LC-MS/MS, LC- Orbitrap / GC-Orbitrap

Significance of PFAS Analysis

Per- and polyfluoroalkyl substances (PFAS) pose significant environmental and health risks due to their persistence and bioaccumulation. Regulatory frameworks in Europe set strict limits for PFAS in drinking water, food, and natural waters, demanding sensitive and reliable analytical methods for trace-level quantification.

Study Overview and Objectives

This work presents three complementary strategies to quantify a wide range of PFAS at low part-per-trillion levels:

• Direct injection on a triple quadrupole mass spectrometer (Thermo Scientific TSQ Altis Plus)
• Automated dispersive liquid-liquid microextraction (DLLME) coupled to high-resolution Orbitrap LC-MS (Exploris MX)
• DLLME with high-resolution Orbitrap GC-MS

The goals include comparing sensitivity, reproducibility, and suitability across clean water and complex matrices such as wastewater, food, and biological samples.

Methodology

Sample Preparation Approaches:

• Direct Injection: Simple dilution of drinking water with internal standards and injection of 100 µL, reducing contamination risk and meeting regulatory LOQs.
• Automated DLLME: Acidified 15 mL sample extracted with water-immiscible solvent and disperser, yielding 30 µL extract (preconcentration factor up to 500) in under 8 minutes per sample.

Chromatographic Conditions:

• Reversed-phase UHPLC on C18 columns with delay column to separate system contaminants and analytes.
• LC gradients optimized for retention of short- and long-chain PFAS (run times 23 min for LC-MS/MS and 17.5 min for LC-HRMS).

Mass Spectrometric Acquisition:

• Triple quadrupole SRM mode for quantitation of 54 PFAS by direct injection.
• Full-scan high-resolution accurate mass (HRAM) on Orbitrap for DLLME extracts, enabling identification and quantitation of 56 PFAS.

Used Instrumentation

• Thermo Scientific TSQ Altis Plus triple quadrupole mass spectrometer with Vanquish Flex UHPLC.
• Thermo Scientific Orbitrap Exploris MX LC-MS system.
• Thermo Scientific Orbitrap Exploris GC system for volatility-compatible PFAS.
• TriPlus RSH SMART automated liquid handler for dispersive microextraction.

Key Results and Discussion

• Sensitivity: Direct injection and DLLME approaches achieved LOQs in the low ng/L to sub-ng/L range, meeting EU 2022/1431 requirements for food and water.
• Matrix Performance: DLLME-HRAM provided 2.5-fold better LOQs for certain PFAS classes (e.g., FASA, FOSE) and consistent quantitation across wastewater, fruits, milk, meat, and eggs.
• Proficiency Testing: Analysis of a FAPAS® drinking water sample yielded results within assigned values using all three strategies, demonstrating method accuracy and robustness.

Practical Applications and Benefits

• High Throughput: Direct injection streamlines routine water testing without extensive cleanup.
• Versatility: DLLME supports diverse matrices with minimal solvent use and reduced environmental impact.
• Cost Efficiency: Both methods eliminate time-consuming solid-phase extraction cartridges and lower sample volume requirements.

Future Trends and Opportunities

Advancements in extraction automation and high-resolution mass spectrometry will drive further improvements in sensitivity and throughput. Emerging PFAS species and transformation products will benefit from HRAM screening workflows. Integration of AI-based data processing can enhance detection confidence and regulatory compliance monitoring.

Conclusion

The combination of direct injection on a triple quadrupole and automated DLLME with Orbitrap mass spectrometry offers a comprehensive PFAS analysis toolkit. These strategies deliver robust, sensitive, and efficient workflows suited for regulatory laboratories, environmental monitoring, and industrial QA/QC.

References

1. Thermo Fisher Scientific Application Note 002902: Direct injection of drinking water for the analysis of 54 PFAS compounds by LC-MS/MS aligned with current and evolving global regulations.
2. Thermo Fisher Scientific Application Brief 003164: Dispersive liquid-liquid micro-extraction for the automated sample preparation of PFAS in drinking water.