QuEChERS Combined with an Agilent 7000 Series Triple Quadrupole GC/MS System for the Analysis of Over 200 Pesticide Residues in Leek and Garlic

Significance of the Topic

Leek and garlic are staple vegetables with proven health benefits, yet their high sulfur content poses analytical challenges. Ensuring accurate monitoring of pesticide residues in these matrices is critical for food safety and regulatory compliance. A rapid, reliable multiresidue method can support routine screening and protect consumer health.

Objectives and Study Overview

This work aimed to develop and validate a streamlined protocol combining QuEChERS sample preparation with Agilent triple quadrupole GC-MS/MS detection to quantify 213 pesticide residues in leek and garlic. Key goals included establishing linear calibration, assessing limits of quantification (LOQs), and demonstrating performance in real market samples.

Methodology and Instrumentation

Sample preparation:

• 10 g minced sample extracted with 10 mL acetonitrile and QuEChERS salts.
• Dispersive SPE cleanup using QuEChERS dSPE kits tailored for each matrix.
• Concentration under nitrogen, reconstitution in ethyl acetate with internal standard.

Instrument setup:

• GC: Agilent 7890A with VF-1701ms column (30 m×0.25 mm, 0.25 µm).
• Oven program: 40 °C hold 1 min; ramp to 120 °C at 40 °C/min; to 240 °C at 5 °C/min; to 300 °C at 12 °C/min, hold 6 min.
• Carrier gas: Helium, 1.0 mL/min; injection: splitless, 1.0 µL.
• MS: Agilent 7000B triple quadrupole, EI source (70 eV), source/interface at 280 °C, Q1/Q2 at 150 °C.

Main Results and Discussion

Method validation demonstrated:

• Linearity over 2–400 µg/kg with R² ≥ 0.99 for most analytes.
• LOQs between 2 and 10 µg/kg; majority at 2 µg/kg, below typical MRLs.
• Recoveries of 80–120% (n = 6) across seven spike levels (2–200 µg/kg) with RSD < 20%.
• Matrix effects varied by compound: ~37% soft, 30% medium, 32% strong enhancement or suppression, highlighting the need for matrix-matched calibration.

Application to eight market samples revealed no detectable residues in garlic and 17 pesticides in leeks. Some levels, including chlorpyrifos and procymidone, exceeded Chinese MRLs, confirming practical relevance.

Benefits and Practical Applications

The optimized approach offers:

• High throughput screening of over 200 pesticides in challenging matrices.
• Simple, reproducible extraction with reduced solvent use and time.
• Low detection limits meeting regulatory requirements.
• Robust quantification via matrix-matched calibration.

Future Trends and Applications

Emerging directions include extending the workflow to additional produce, integrating automated or online cleanup, and leveraging high-resolution MS for broader target screening. Further refinement of sorbent materials and miniaturized extraction may enhance sustainability.

Conclusion

The presented QuEChERS-GC-MS/MS method delivers reliable, sensitive multiresidue analysis of 213 pesticides in leek and garlic. Its strong validation metrics and successful real-sample application support its adoption for routine monitoring in food safety laboratories.

Reference

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