Determination of organochlorine pesticides (OCPs) in soils using the EXTREVA ASE Accelerated Solvent Extractor and GC-ECD

Significance of the topic

The widespread historical use of organochlorine pesticides (OCPs) and their persistence in soil demand reliable analytical methods to monitor environmental contamination and ensure compliance with regulatory thresholds. High-throughput, sensitive, and reproducible protocols help laboratories manage large sample loads while minimizing solvent waste and operator time.

Study objectives and overview

This study presents a streamlined method for the determination of 20 OCPs in soil matrices. It combines the Thermo Scientific™ EXTREVA™ ASE™ Accelerated Solvent Extractor system with GC–ECD detection, following U.S. EPA guidelines, to demonstrate fully automated extraction, concentration, and analysis in a single workflow.

Methodology and instrumentation

Sample preparation and extraction were performed using the EXTREVA ASE system under optimized conditions (100 °C, 200 psi, acetone–hexane 1:1, gas-assisted extraction). Key instrumentation and materials included:

• EXTREVA ASE Accelerated Solvent Extractor (Thermo Fisher Scientific)
• TRACE™ 1310 Gas Chromatograph with Electron Capture Detector
• 10 mL and 100 mL stainless-steel ASE cells with cellulose filters and dispersants
• Standards: organochlorine pesticide mix, surrogate and internal standards
• Solvents: Optima™ hexanes and acetone

GC–ECD conditions featured a split‐PTV injector, Rtx-CLPesticides column (30 m × 0.25 mm × 0.25 µm), helium carrier gas, and a temperature program from 120 °C to 300 °C.

Main results and discussion

Recovery experiments at 25 µg/kg spike levels showed:

• Average recoveries of 80–115% for all OCPs, meeting U.S. EPA acceptance criteria
• Relative standard deviations below 8%, indicating high reproducibility
• Carryover below 0.5% after solvent rinsing protocols
• Thermal degradation of thermolabile compounds (endrin, DDT) under typical extraction temperatures remained below 5%

The integrated evaporation step achieved solvent exchange from acetone to hexane and final volumes of 1 mL with minimal analyte loss (<15%).

Benefits and practical applications

This approach delivers:

• Full automation of extraction and concentration (“load-and-go”), reducing manual handling
• Significant solvent and time savings compared to Soxhlet or sonication
• Unattended operation with parallel processing of up to 16 samples
• Compliance with stringent regulatory methods (EPA 8081B, 8270E)

It is well suited for environmental laboratories engaged in routine soil screening, QA/QC of remediation sites, and regulatory compliance testing.

Future trends and opportunities

Advancements may include:

• Integration with AI-driven instrument control and real-time data analytics
• Extension to other persistent organic pollutants and emerging contaminants
• Miniaturized ASE cell formats for further solvent reduction
• Remote operation and cloud-based data management via chromatography data systems

Conclusion

The EXTREVA ASE system combined with GC–ECD offers a robust and efficient platform for determining OCPs in soil. Its fully automated extraction and concentration workflow ensures high recoveries, low variability, minimal carryover, and enhanced laboratory throughput, meeting modern environmental analysis demands.

References

• United Nations Environment Programme. Stockholm Convention on Persistent Organic Pollutants, 2001.
• United States Environmental Protection Agency. Method 8270E: Semivolatile Organic Compounds by GC–MS, 2014.
• United States Environmental Protection Agency. Method 8081B: Organochlorine Pesticides by Gas Chromatography, 2007.
• United States EPA. SW-846 Test Method 3545A: Pressurized Fluid Extraction (PFE), 2010.
• Srinivasan, K. and Ullah, R. Method and Device to Extract Analyte from a Sample with Gas Assistance. US Patent No. 9,440,166 B2 (2016).
• Srinivasan, K. and Ullah, R. Apparatus for Parallel Accelerated Solvent Extraction. US Patent No. 11,123,655 B2 (2021).