Simultaneous routine GC-MS analysis of PCBs, PAHs, and their derivatives in soil using modified QuEChERS methodology

Significance of the Topic

Polychlorinated biphenyls and polyaromatic hydrocarbons are resilient organic pollutants that accumulate in soils and pose significant health and environmental risks. Oxidized and heterocyclic derivatives of PAHs have prompted expanded monitoring due to comparable or greater toxicity. Efficient, high throughput soil analysis methods are essential to ensure timely risk assessment and regulatory compliance.

Objectives and Study Overview

This study evaluates the quantitative performance of a modified QuEChERS method combined with the Thermo Scientific ISQ 7000 single quadrupole GC-MS system featuring the ExtractaBrite electron ionization source and NeverVent Technology. Key goals include achieving comprehensive analysis of PCBs, PAHs and their derivatives in a single rapid run under 20 minutes while maintaining sensitivity, selectivity, linearity and robustness for routine environmental monitoring.

Methodology

Freeze dried, homogenized soil was spiked with isotopic internal standards and extracted using a modified QuEChERS protocol with DCM acetone, salt extraction and dSPE cleanup. Extracts were dried under nitrogen, fortified with a syringe standard and reconstituted in n-hexane. Quantification standards spanned 0.1 to 500 pg uL covering 45 native analytes and 14 labeled internal standards.

Instrumentation Used

• Thermo Scientific TRACE 1310 GC with NeverVent technology
• Thermo Scientific ISQ 7000 single quadrupole GC-MS with ExtractaBrite EI source
• Thermo Scientific TRACEGOLD TG-5 SilMS capillary column 30 m x 0.25 mm x 0.25 um
• AI AS 1310 Series Autosampler
• Chromeleon 7.2 CDS software for acquisition and processing

Key Results and Discussion

• Complete separation of 45 analytes in under 20 minutes including critical PAH pairs
• Instrument detection limits of 0.06 to 2.00 ug kg and method quantification limits of 0.4 to 5.0 ug kg in soil
• Linearity across 0.1 to 500 pg uL with R2 greater than 0.998 and response factor RSD under 10 percent
• Average internal standard recovery of 75 percent and extraction precision under 15 percent RSD
• Effective selectivity in complex soil matrices and no significant carryover with optimized needle wash solvents
• Accurate quantification of native residues at sub microgram per kilogram levels with ion ratio deviations within acceptance criteria

Benefits and Practical Applications

• Consolidation of PAHs PCBs and derivatives into a single rapid method reducing labor and instrument demands
• Sample preparation time reduced to 2 hours compared to 24 to 48 hour Soxhlet extractions
• Up to twentyfold increase in throughput and lower cost per sample
• Improved laboratory productivity through rapid column exchanges and minimal source maintenance

Future Trends and Potential Applications

• Expansion to emerging PAH derivatives NSO PAHs and other persistent pollutants
• Integration with high resolution mass spectrometry for non target screening
• Automated data processing using advanced eWorkflows and artificial intelligence
• Adoption of greener solvents and miniaturized extraction techniques
• Application to additional matrices such as sediments and airborne particulate matter

Conclusion

The combination of a modified QuEChERS extraction with the ISQ 7000 GC MS system and NeverVent Technology offers a fast sensitive and robust workflow for routine soil analysis of PCBs PAHs and derivatives delivering reliable quantitative performance and significant time and cost savings for environmental laboratories.

References

• CEN TR 16998 2016 Ambient air – Report on nitro and oxy PAHs – Origin toxicity concentrations and measurement methods
• Sun Z et al Occurrence of nitro and oxy PAHs in agricultural soils in eastern China and excess lifetime cancer risks from human exposure through soil ingestion Environ Int 2017 108 261–270
• Anderson JT Achten C Time to say Goodbye to the 16 EPA PAHs Toward an up to date use of PACs for environmental purposes Polycyclic Aromatic Compounds 2015 35 330–354
• Thermo Scientific Technical Note 10721 Routine and robust analysis of PAHs and PCBs in soil by single quadrupole GC MS 2019
• Thermo Scientific Application Note 21735 Ultra inert low bleed GC columns with advanced silphenylene polymer technology 2017