Non-targeted analysis of PFAS using two-dimensional gas chromatography (GC×GC)

Non-Targeted PFAS Analysis Using GC×GC

Importance of the Topic:
Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants associated with polymer production and specialized applications such as plastic-bonded explosives (PBXs). Their structural diversity and low concentrations present analytical challenges for detection and fingerprinting. Developing robust non-targeted methods enables comprehensive profiling of known and unknown PFAS in technical materials and environmental samples, supporting safety, regulatory compliance, and pollution prevention.

Objectives and Study Overview:
The study aimed to develop non-targeted workflows for PFAS detection, characterize fluoropolymer binders in PBXs, and extend fingerprinting approaches to environmental matrices.

Methodology and Instrumentation:
• Sample Preparation:

• Extraction of fluoropolymers with solvent mixtures (THF, ethyl acetate, methanol, acetone, water blends).
• Optimization showed strong organic solvents were required to liberate PFAS from polymer matrices.

• Chromatographic Analysis:

• UHPLC-QTOF for targeted and broad-spectrum PFAS screening.
• GC-TOFMS with thermal desorption and cryotrap injection to improve solvent masking and focus volatile PFAS.
• Comprehensive two-dimensional GC (GC×GC) coupled with TOFMS and high-resolution MS (HRMS) for enhanced separation and selectivity.

Instrumentation Used:

• UHPLC coupled to triple quadrupole and quadrupole time-of-flight MS.
• GC-TOFMS with thermal desorption inlet and cryogenic focusing.
• GC×GC-TOFMS and GC×GC-HRMS systems.

Key Results and Discussion:

• THF and ethyl acetate mixtures proved essential for complete dissolution of fluoropolymers and PFAS release.
• TD-GC-TOFMS revealed complex PFAS profiles in Kel-F 800, including multiple isomers and unknown components.
• GC×GC provided enhanced chromatographic resolution but still required HRMS to resolve coeluting species.
• High-resolution accurate mass data enabled Kendrick mass defect analysis, uncovering hundreds of PFAS-like features beyond the target list.

Benefits and Practical Applications:

• Non-targeted GC×GC-HRMS workflows capture both regulated and novel PFAS, increasing detection scope.
• Fingerprinting of fluoropolymer lots supports source attribution, quality control, and legacy material assessment.
• Approach can be transferred to environmental monitoring around PFAS sources such as explosives facilities.

Future Trends and Opportunities:

• Further optimization of GC×GC-HRMS separation parameters to maximize PFAS coverage.
• Adaptation of Kendrick mass defect workflows for automated non-targeted PFAS discovery.
• Development of AI/ML models for rapid fingerprinting of diverse fluoropolymer lots and environmental samples.
• Investigation of PFAS emissions during PBX disposal and degradation pathways in natural settings.

Conclusion:
Comprehensive non-targeted GC×GC-HRMS methods expand the analytical window for PFAS in complex matrices such as fluoropolymer-bound explosives. These workflows enable in-depth chemical fingerprinting, support environmental risk assessment, and pave the way for advanced data analytics in PFAS research.