Determination of polychlorinated biphenyls (PCBs) in soils using a new fully automated parallel extraction and evaporation system and GC-MS

Importance of the topic

Polychlorinated biphenyls are persistent organic pollutants that resist degradation and bioaccumulate in soil, water, and living organisms. Despite their ban decades ago, PCBs remain a global concern due to their toxicity and potential to enter the food chain. Reliable and rapid analysis of PCBs in soils is essential for environmental monitoring, regulatory compliance, and remediation efforts.

Objectives and study overview

This study presents a streamlined analytical protocol for quantifying 17 PCB congeners in soil using a fully automated parallel extraction and evaporation system coupled with gas chromatography–mass spectrometry. The goal was to demonstrate method performance, including recovery, precision, carryover, and compliance with established regulatory guidelines.

Methodology and instrumentation

Sample prep relied on accelerated solvent extraction with in situ evaporation. Soil samples were mixed with dispersants and loaded into stainless steel cells of two sizes. A gas-assisted delivery system brought hexane to 100 degrees under controlled pressure for efficient extraction. Extracts were concentrated to a fixed volume under nitrogen and transferred to autosampler vials. GC–MS analysis employed splitless injection, a midpolarity column, temperature programming from 100 to 310 degrees, and timed selected ion monitoring to optimize sensitivity.

Used instrumentation

• EXTREVA ASE accelerated solvent extractor with parallel gas assisted extraction and evaporation
• TRACE 1310 gas chromatograph with TG-5MS column
• ISQ single quadrupole mass spectrometer in electron ionization mode

Results and discussion

Recovery experiments at 100 micrograms per kilogram spike level produced mean recoveries between 77 and 101 percent with relative standard deviations below 10 percent, meeting or exceeding regulatory acceptance ranges. Evaporation tests showed minimal analyte loss and robust solvent exchange capabilities. Carryover remained below 0.5 percent after high-level spikes, confirming effective system rinsing. Analysis of a certified reference soil yielded concentrations within certified limits for all target congeners, demonstrating method accuracy and reproducibility.

Benefits and practical applications

The integrated extraction and evaporation workflow eliminates manual steps, reduces solvent usage by up to 50 percent, and supports unattended operation. Parallel processing of up to four samples accelerates throughput and minimizes laboratory labor, making it suitable for environmental, industrial, and regulatory testing laboratories.

Future trends and potential applications

Advances may include integration with liquid chromatography for broader compound coverage, further miniaturization to reduce solvent and sample requirements, and AI-driven method optimization for complex matrices. The principles demonstrated here could be extended to emerging contaminants such as halogenated flame retardants and perfluorinated compounds.

Conclusion

The combined use of a fully automated ASE and GC–MS provides a robust, precise, and efficient protocol for PCB analysis in soils. Method performance meets regulatory criteria while offering significant time and solvent savings. This approach enhances laboratory efficiency and supports high-quality environmental monitoring.

References

• US EPA Method 3540C
• US EPA Method 3550C
• US EPA Method 3546
• US EPA Method 3545A
• Patent US9440166 B2
• Patent US11123655 B2