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

Importance of the topic

PFAS are persistent and bioaccumulative compounds that pose risks to human health and the environment. Accurate and sensitive analysis of PFAS at trace levels is essential to support regulatory compliance and risk assessment.

Objectives and overview of the study

This study compares direct injection on a triple quadrupole mass spectrometer with automated dispersive liquid-liquid microextraction (DLLME) coupled to high-resolution Orbitrap mass spectrometry and GC-Orbitrap for PFAS analysis. The goal is to evaluate sensitivity, throughput, and applicability across diverse matrices.

Methodology and instrumentation

• Direct injection workflow
  
  • Instrument: Thermo Scientific TSQ Altis Plus triple quadrupole
  • Injection volume: 100 µL
  • Chromatographic run time: 23 minutes (SRM acquisition)
• Automated DLLME workflow
  
  • Automated handling: TriPlus RSH SMART liquid handling station
  • Instruments: Orbitrap Exploris MX (LC-HRMS) and Orbitrap Exploris GC
  • Injection volume: 10 µL; run time: 17.5 minutes (full-scan acquisition)
  • Key steps: pH adjustment, solvent selection and ratio, secondary extraction to achieve up to 500× pre-concentration

Used instrumentation

• Thermo Scientific Vanquish Flex UHPLC system
• Acclaim 120 C18 analytical and delay columns
• Thermo Scientific TSQ Altis Plus triple quadrupole mass spectrometer
• Thermo Scientific Orbitrap Exploris MX high-resolution mass spectrometer
• Thermo Scientific Orbitrap Exploris GC system
• TriPlus RSH SMART automated liquid handling station

Main results and discussion

• Direct injection achieved quantitation limits of 0.25 to 1 ng/L for a broad PFAS range with R2 > 0.99.
• DLLME-HRAM improved detection limits to 0.1–0.5 ng/L, enabling ppt-level quantification of 56 PFAS from 15 mL samples.
• FAPAS proficiency testing showed close agreement with assigned values for PFHxS, PFOA, PFOS and PFNA across all strategies.
• DLLME-HRAM provided over 2.5× sensitivity gains for certain PFAS classes compared to direct injection.
• Both workflows meet or exceed EU regulatory LOQs for food, water and biological matrices.

Benefits and practical applications

• Direct injection: rapid sample throughput, minimal contamination risk, simple dilution workflow suitable for routine drinking water monitoring.
• DLLME: versatile extraction for water, food, soil and biological samples, high pre-concentration, reduced solvent consumption and waste.
• Automated DLLME supports high throughput and reproducibility with standardized SOPs.
• Lower operational costs and environmental impact by eliminating SPE cartridges and reducing solvent volumes.

Future trends and potential applications

• Expansion of HRMS-based workflows for multiplexed PFAS screening in environmental and food safety applications.
• Integration of miniaturized extraction platforms and ambient ionization techniques for on-site monitoring.
• Development of standardized automated protocols to support global regulatory harmonization and large-scale monitoring programs.

Conclusion

Both direct injection on a triple quadrupole and automated DLLME coupled to Orbitrap platforms offer robust, sensitive and efficient strategies for trace-level PFAS analysis. The choice depends on the required detection limits and sample matrix complexity, with DLLME-HRAM providing the highest sensitivity and matrix versatility.

Reference

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.