Determination of Multiclass, Multiresidue Pesticides in Tree Nuts by Captiva EMR–LPD Passthrough Cleanup and LC/MS/MS

Significance of the topic

Tree nuts are rich in heart-healthy unsaturated fats, phytochemicals and antioxidants, but their high lipid content and complex matrix pose challenges for sensitive multi-residue pesticide analysis. Reliable monitoring ensures food safety and compliance with regulatory limits, protecting consumers and maintaining product quality.

Goals and Study Overview

This work developed and optimized a streamlined workflow to detect 125 LC-amenable pesticides in almonds, pecans, cashews and hazelnuts. Key objectives included simplified sample cleanup, minimized matrix effects, and robust quantitation performance using QuEChERS AOAC extraction, Captiva EMR–LPD passthrough cleanup and LC/MS/MS analysis.

Methodology and Instrumentation

Sample preparation combined an Agilent Bond Elut QuEChERS AOAC extraction kit with an Agilent Captiva EMR–LPD cartridge for direct cleanup. After hydrating the crude acetonitrile extract with 10% water, a low-pressure passthrough removed lipids and fatty acids. Cleanup eluents were diluted and injected onto an Agilent 1290 Infinity UHPLC coupled to an Agilent 6490 triple quadrupole mass spectrometer operating in both positive and negative ESI modes.

Used Instrumentation

• Agilent 1290 Infinity binary pump, autosampler, column compartment
• Agilent 6490 triple quadrupole LC/MS with Jet Stream ESI source
• Agilent MassHunter Workstation software
• Bond Elut QuEChERS AOAC extraction kit and Captiva EMR–LPD cartridges
• Centrifuge, Geno/Grinder, shaker, positive-pressure manifold

Main Results and Discussion

Method optimization included comparing buffered AOAC vs. EN salts, and varying water premixing before cleanup. Key findings:

• AOAC buffered salts improved recoveries of acid-sensitive pesticides by up to 30%.
• Adding 10% water before EMR–LPD cleanup maximized recoveries and lipid removal; 20% water reduced efficiency.
• GC/MS full scan and dried residue measurements showed >64% co-extractive removal across tree nuts (up to 85% in almonds).
• Quantitation performance met SANTE criteria: over 85% of targets had recoveries of 70–120%, >64% exhibited RSDs <10%, and >86% showed negligible matrix effects (80–120%).
• Matrix-matched calibration achieved linear ranges of 1–1,000 ng/g (2.5–2,500 ng/g in hazelnuts) with R² values typically >0.99.

Benefits and Practical Application

This workflow delivers:

• Rapid, one-step passthrough cleanup without dispersive SPE or freezing steps
• High lipid and fatty acid removal for improved instrument uptime
• Reliable quantitation across a wide pesticide panel in challenging nut matrices
• Reduced sample handling time and enhanced laboratory throughput

Future Trends and Possibilities

Emerging directions include:

• Expansion to other high-fat or pigment-rich commodities
• Integration with high-resolution MS for non-targeted screening
• Automation of passthrough cleanup in 96-well and inline formats
• Application of novel sorbent chemistries for ultra-trace analyses

Conclusion

The combined QuEChERS AOAC extraction and Captiva EMR–LPD cleanup method offers a fast, reliable and effective solution for multi-residue pesticide analysis in tree nuts. It ensures excellent matrix removal, robust recoveries, reproducibility and quantitation across 125 compounds, supporting high-throughput routine testing.

References

• Zhao L.; Wei T. Determination of Multiclass, Multiresidue Pesticides in Spring Leaf Mix Using Captiva EMR–HCF Passthrough Cleanup and LC/MS/MS, Agilent Technologies application note, 5994-5765EN, 2022.
• SANTE/11312/2021. Analytical Quality Control and Method Validation Procedures for Pesticide Residues Analysis in Food and Feed.