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

Importance of the Topic

Cereal grains such as corn, wheat flour, and rice are staple foods worldwide and can accumulate residues from more than 200 pesticides applied during cultivation. Reliable, high-throughput analytical methods are essential to verify compliance with regulatory maximum residue limits (MRLs), ensure food safety, and support routine monitoring in food control laboratories.

Objectives and Study Overview

This study aimed to develop and validate a streamlined multiresidue method that combines a modified QuEChERS extraction workflow with Agilent 7000 series triple quadrupole GC/MS for the simultaneous determination of 218 pesticides in cereal matrices. Matrix-matched calibration was implemented to compensate for matrix effects and achieve accurate quantification over a broad concentration range.

Methodology

A 5 g aliquot of homogenized cereal sample was hydrated with water, extracted with acetonitrile containing 1 % acetic acid and QuEChERS salt in a ceramic homogenizer, and centrifuged. A portion of the extract underwent dispersive solid phase cleanup, evaporation under nitrogen, and reconstitution in ethyl acetate before analysis. Six fortification levels (5, 10, 20, 50, 100, 200 µg/kg) were used for method validation including recovery and precision assessment.

Instrumentation

• Gas chromatograph: Agilent 7890A with 7693A autosampler
• Column: VF-1701ms, 30 m × 0.25 mm, 0.25 µm film
• Injection: splitless at 280 °C, 1 µL volume, helium carrier at 1.0 mL/min
• Oven program: 40 °C (1 min), ramp 40–120 °C at 40 °C/min, 120–240 °C at 5 °C/min, 240–300 °C at 12 °C/min (hold 6 min)
• Mass spectrometer: Agilent 7000B triple quadrupole GC/MS, EI at 70 eV, Q1/Q2 at 150 °C, interface 280 °C, specific MRM transitions optimized per analyte

Main Results and Discussion

Linearity across 2–200 µg/L in matrix-matched standards achieved R2 ≥ 0.99 for 97 % of pesticides. Limits of quantification (LOQs) ranged from 5 to 50 µg/kg, with most targets validated at 5 µg/kg. Recovery tests (n = 6) at six levels showed 70–120 % recoveries and RSDs < 20 % for the majority. A few compounds exhibited recoveries or precision slightly outside criteria at the lowest levels. Ten commercial cereal samples revealed two trace residues well below MRLs, demonstrating method applicability to real matrices.

Benefits and Practical Applications

• High throughput screening of over 200 pesticide residues in cereals
• Simplified sample preparation with ceramic homogenizer and reduced cleanup steps
• Sensitive and accurate quantification below regulatory limits
• Robust performance suitable for routine quality control and residue monitoring

Future Trends and Potential Applications

Further expansion of compound scope, integration with high-resolution MS for non-target screening, automation of sample handling, and adaptation to other complex food and feed matrices are promising directions. Miniaturized QuEChERS formats and online coupling with GC/MS may enhance throughput and reduce solvent use.

Conclusion

The validated QuEChERS-GC/MS/MS workflow provides a rapid, reliable, and sensitive approach to quantifying a broad panel of 218 pesticide residues in cereal grains. Its high recoveries, low LOQs, and robust precision make it well suited for regulatory compliance and routine food safety surveillance.

References

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