Analysis of Persistent Organic Pollutants in Complex Matrices by Gas Chromatography—High Resolution Time-of-Flight Mass Spectrometry

Importance of the topic

Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) pose serious environmental and health risks due to their bioaccumulation and persistence. Regulatory agencies worldwide demand reliable identification and quantification of these compounds in complex environmental and biological matrices. High-resolution gas chromatography–time-of-flight mass spectrometry (GC-HRT) offers the selectivity, mass accuracy and resolving power needed to overcome challenges related to low analyte concentrations, matrix interferences, and isobaric overlaps.

Objectives and study overview

This study demonstrates the application of the LECO Pegasus® GC-HRT system with Folded Flight Path™ (FFP™) technology to achieve both targeted and non-targeted screening of POPs. Sediment and fish tissue samples were examined for PCB congeners as primary targets, while additional POP classes were discovered through comprehensive full-scan acquisition. The goal was to assess resolving power, mass accuracy and library match quality in both high-resolution and ultra-high-resolution modes.

Methodology

• Sample preparation involved solvent extraction (dichloromethane:hexane, 1:4 v/v), silica cleanup and concentration to isooctane.
• Gas chromatography used a Restek Rxi-5Sil MS column (60 m × 0.18 mm × 0.10 µm) with splitless injection (1 µL at 300 °C) and an oven program from 80 °C to 300 °C.
• Mass spectrometry data were acquired in two modes: high resolution (R ≈ 25 000 FWHM) and ultra-high resolution (R ≈ 50 000 FWHM) at m/z ≈ 219, covering m/z 50–1000 (HR) and 200–600 (UHR).
• Acquisition rate was set to three spectra per second, calibrated using perfluorotributylamine (PFTBA).

Used instrumentation

• LECO Pegasus® GC-HRT with FFP™ mass analyzer
• Agilent 7890 GC and 7693 autosampler
• Restek Rxi-5Sil MS capillary column
• Helium carrier gas at 1.0 mL/min constant flow
• Electron ionization source (70 eV, positive polarity)

Main results and discussion

In sediment samples, deconvolution and library searches identified key PCB congeners (CB 47, CB 162, CB 209) with match scores above 800 and sub-ppm mass accuracy. Extracted ion chromatograms and isotope-pattern correlations confirmed compound identities. Fish tissue analysis revealed 70 PCB congeners with an average mass error of ~1.0 ppm. Ultra-high-resolution mode enabled clean separation of isobaric fragments, notably distinguishing BDE 47 from CB 180. Comprehensive screening also detected additional POP classes in fish extracts, including hexachlorobenzene, octachlorostyrene, DDMU, p,p’-DDE, DDT and other brominated and chlorinated species with precise mass assignments.

Benefits and practical applications

• Single-run screening of multiple POP classes without separate methods
• High mass accuracy and resolution support unambiguous elemental composition determination
• Library-search capability enables rapid confirmation of both targeted and non-targeted analytes
• Ultra-high-resolution mode resolves coeluting or isobaric interferences, improving quantitative reliability

Future trends and applications

Further integration of high-resolution GC-TOF MS with advanced data processing and non-targeted workflows will expand the scope of environmental monitoring. Emerging informatics platforms and machine learning models can leverage accurate mass data to discover new contaminants of concern. Ongoing improvements in speed, resolving power and user-friendly interfaces will support routine QA/QC and regulatory compliance in diverse laboratories.

Conclusion

The LECO Pegasus GC-HRT system demonstrates robust performance for targeted and exploratory analysis of persistent organic pollutants in challenging sample types. Its combination of high resolving power, accurate mass measurement and full-scan capability streamlines comprehensive POP profiling, meeting stringent demands of environmental and food safety laboratories.

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