Application of Nexera UC SFE Pretreatment System for Extracting Pesticide Residues from Soil

Significance of the Topic

Assessing pesticide residues in soil is critical for environmental safety, regulatory compliance and sustainable agriculture. Traditional liquid–liquid extraction methods are time-consuming, use large volumes of organic solvents and can introduce contaminants or degrade target analytes. Supercritical fluid extraction (SFE) with CO₂ offers rapid, efficient and greener sample preparation, improving laboratory throughput and minimizing environmental impact.

Study Objectives and Overview

This work evaluates the Nexera UC SFE pretreatment system for extracting eight representative pesticides from soil. Key goals include:

• Demonstrate a simplified sample preparation workflow requiring minimal solvent and handling.
• Optimize SFE parameters (temperature, pressure, flow) for efficient recovery.
• Assess repeatability and extraction recovery compared to conventional methods.
• Integrate with LC-MS/MS analysis to quantify trace pesticides within 30 minutes per sample.

Methodology and Instrumentation

Sample Preparation and Extraction Workflow:

1. Mix 1 g of air-dried soil with 1 g of a dehydrating agent and load into a 5 mL extraction vessel.
2. Heat vessel to 40 °C; pressurize with CO₂ to 15 MPa for static extraction (4 min).
3. Switch to dynamic mode: pump supercritical CO₂ (5 mL/min) with methanol modifier through the vessel.
4. Trap eluted analytes on a VP-ODS guard column; depressurize and collect eluate into fraction tubes.

Post-Extraction Processing and Analysis:

• Dilute collected eluate to 2 mL with acetone/hexane (1:1) for cleanup.
• Inject 3 µL into a Shim-pack UC-RP column (150 × 2.1 mm, 3 µm) using a Nexera X2 LC system.
• Perform gradient elution with 10 mM ammonium formate in water to methanol (0–100% B over 17 min) at 0.4 mL/min and 40 °C.
• Detect pesticides via LCMS-8060 in MRM mode with ESI (positive/negative).

Instrumentation Used

• Nexera UC SFE Pretreatment System with CO₂ pump and back-pressure regulator
• Shim-pack VP-ODS trap column and Shim-pack UC-RP analytical column
• Nexera X2 UHPLC system
• LCMS-8060 triple quadrupole mass spectrometer
• Rack changer enabling up to 48 sequential extractions

Main Results and Discussion

Extraction performance was evaluated for alachlor, atrazine, diflufenican, fipronil, flumioxazin, fluxapyroxad, pyraclostrobin and trifloxystrobin spiked at 200 ng/g:

• Repeatability (n=6) showed RSD values between 1.2% and 3.8%, indicating high precision.
• Recovery rates ranged from 70% to 88%, comparable to or exceeding those of liquid–liquid extraction.
• Total pretreatment time was approximately 30 min per sample, significantly faster than conventional methods.
• Chromatograms displayed sharp, well-resolved peaks with minimal background, reflecting efficient cleanup by SFE.

Benefits and Practical Applications

• Reduced use of organic solvents enhances laboratory safety and lowers disposal costs.
• Shortened extraction times increase sample throughput in environmental monitoring or QA/QC labs.
• Automated rack changer minimizes operator intervention and human error.
• Gentle SFE conditions prevent analyte degradation and instrument contamination.
• Applicability to a broad range of semi-volatile and non-polar pesticides in soil matrices.

Future Trends and Opportunities

• Integration of online SFE-LC/MS workflows for real-time analysis and faster decision-making.
• Development of customizable SFE modifiers and trap chemistries for polar and ionic compounds.
• Expansion to other environmental matrices such as sediments, sludge or foodstuffs.
• Advances in miniaturized SFE instrumentation for field-deployable monitoring.
• Enhanced data analytics and AI-driven method optimization for complex sample sets.

Conclusion

The Nexera UC SFE pretreatment system delivers a rapid, precise and eco-friendly approach for extracting pesticide residues from soil. High recoveries, excellent repeatability and reduced solvent consumption make this workflow well suited for environmental laboratories and regulatory testing. By coupling SFE with LC-MS/MS, analysts achieve reliable results in under 30 minutes, supporting efficient monitoring of soil contamination.

References

• Shimadzu Application Note L503
• Miyazaki Hydro-Protect Patent No. 3645552