An Optimal Method for the Analysis of Pesticides in a Variety of Matrices

Importance of the Topic

Analysis of pesticide residues across diverse agricultural and environmental matrices is critical to ensure food safety and regulatory compliance. High-throughput, sensitive methods allow quantification of hundreds of compounds at trace levels, mitigating risks posed by matrix interferences and evolving pesticide chemistries.

Objectives and Study Overview

This study aimed to develop an optimized GC–MS/MS method for simultaneous determination of a broad panel of pesticides in eight distinct matrix categories. Key goals included evaluation of matrix effects on MRM transitions, validation of limits of quantitation at low picogram per microliter levels, and demonstration of a workflow applicable to routine analytical laboratories.

Methodology and Instrumentation

Sample preparation followed QuEChERS protocols tailored to each matrix, including high-oil (olive oil), high-pigment (black tea, spinach), high-starch (rice), high-water (cucumber), high-sugar (honey), high-acid (orange), and clean matrices (onion). Combined techniques ensured efficient extraction and cleanup. Chromatographic separation employed an Agilent 7890B GC with an ultra-inert multimode inlet and dual HP-5ms UI columns connected via a purged ultimate union enabling backflushing. The mass spectrometer was an Agilent 7010 Triple Quadrupole GC/MS in MRM mode.

• Injection volume: 1 µL hot splitless at 280 °C
• Oven program: 40 °C/min to 120 °C, then 5 °C/min to 310 °C
• Carrier gas: He, constant flow 1.00/1.20 mL/min
• Electron energy: 70 eV, MS1 and MS2 resolution: wide
• Backflush: initiated post-run for 1.5 minutes to maintain column performance

Main Results and Discussion

The optimized method achieved low-ppb detection in complex extracts. Calibration curves (0.12–50 pg/µL) yielded R2 ≥ 0.990 for 90% of compounds. Repeatability studies showed ≤ 30% RSD, and 90% of analytes had LOQs ≤ 1.5 pg/µL. Matrix-dependent shifts in MRM responses were observed, particularly in tea and spinach, underscoring the need for matrix-optimized MRM selection. By evaluating up to 10 transitions per compound, analysts could select the most robust quantifier and qualifier pairs that met ion-ratio criteria and minimized interference.

Benefits and Practical Applications

Implementing this method allows laboratories to:

• Confirm pesticide residues at low concentration levels within diverse sample types.
• Improve throughput by reducing reanalysis due to matrix interferences.
• Customize MRM transitions based on matrix-specific performance for reliable quantitation.

Future Trends and Opportunities

As regulatory demands and pesticide chemistries evolve, future developments may include expansion of MRM libraries to cover novel compounds, integration of high-resolution MS for untargeted screening, and automation of method optimization using machine learning approaches. Further work could refine sample preparation for emerging matrix types and enhance sensitivity through column and inlet technology advancements.

Conclusion

The described GC–MS/MS workflow, supported by a comprehensive MRM database, offers a robust template for multi-residue pesticide analysis across complex matrices. Matrix-optimized MRM selection and method validation ensure confident detection at trace levels, addressing both analytical and regulatory challenges.

Reference

Westland J. An Optimal Method for the Analysis of Pesticides in a Variety of Matrices. NACRW 2016. Agilent Technologies. P-070.