Enhanced sensitivity for the quantitative analysis of pesticides using a GC Orbitrap MS

Importance of the topic

Reliable, sensitive detection of pesticide residues in food matrices is essential to protect public health and comply with regulatory limits. Complex or highly pigmented matrices such as spinach challenge conventional GC–MS approaches because matrix interferences can mask analytes, produce false positives or reduce sensitivity. High-resolution accurate-mass full-scan GC–Orbitrap workflows enable selective identification and robust quantitation of trace-level pesticide residues while also supporting retrospective screening for additional or emerging compounds.

Study objectives and overview

This study evaluated the Thermo Scientific Orbitrap Exploris GC S mass spectrometer, equipped with the NeverVent Advanced Electron Ionization (NVAEI) source, for quantitative multiresidue pesticide analysis in QuEChERS extracts of spinach. Key aims were to assess sensitivity (IDLs), linearity over a wide range, spectral fidelity and mass accuracy, compliance with SANTE criteria for identification and quantitation, and practical robustness for routine laboratory use. A mixture of 185 pesticides was used for post-spiking experiments in purified spinach extracts to simulate a challenging, pigmented matrix.

Methodology

The analytical workflow combined acetonitrile QuEChERS extraction of spinach with GC electron ionization (EI) full-scan high-resolution accurate-mass (FS-HRAM) acquisition on the Orbitrap Exploris GC S. Method validation elements included:

• Matrix-matched calibration over 0.5–200 µg/kg with triplicate injections at each level.
• Replicate injections of low-level matrix-matched standards to calculate instrumental detection limits (IDLs).
• Assessment of spectral fidelity across concentrations (examples at 1 and 200 µg/kg) and long-term mass accuracy over a four-week period.
• System suitability checks using criteria derived from SANTE/11312/2021 (identification by two ions ≤5 ppm mass error, retention time tolerance ±0.1 min; ion ratio deviation ±30% considered supportive).

Instrumentation used

The principal instrumentation and software components reported were:

• Thermo Scientific Orbitrap Exploris GC S mass spectrometer with NeverVent Advanced Electron Ionization (NVAEI) source.
• Gas chromatography with EI ionization configured for full-scan HRAM acquisition (m/z 50–600).
• Sample preparation: acetonitrile QuEChERS extracts of spinach, purified and post-spiked with pesticide mix.
• Data acquisition and processing: Thermo Scientific Chromeleon Chromatography Data System (CDS) with capabilities for automated workflows, sequence reprocessing and compliance with FDA 21 CFR Part 11 and EU Annex 11.

Main results and discussion

The Orbitrap Exploris GC S demonstrated strong analytical performance for the tested multiresidue pesticide set in a pigmented spinach matrix:

• Sensitivity: Calculated IDLs showed that most pesticides reached detection limits at or below 0.5 µg/kg.
• Linearity and quantitative precision: Matrix-matched calibration over 0.5–200 µg/kg produced coefficients of determination R² > 0.993 for all targets; response-factor %RSD across the range was <20%.
• System suitability and recoveries: Calculated concentrations were within ±20% of expected values and recoveries ranged 96–104%.
• Identification criteria: All targets met SANTE acceptance at the default MRL of 10 µg/kg and over 90% were confirmed at 1 µg/kg when applying the guidance (two ions ≤5 ppm, RT ±0.1 min; ion ratios used as supportive evidence within ±30%).
• Spectral fidelity and mass accuracy: The instrument produced consistent, high-quality EI spectra across concentration levels. Examples showed near sub-1 ppm mass accuracy for specific molecular ion clusters at low and high concentrations; average mass error across calibration levels remained within ca. 3 ppm. Stability of mass accuracy was maintained over four weeks, supporting long-term robustness.
• Operational advantages: FS-HRAM acquisition enabled simultaneous targeted quantitation and non-targeted screening with retrospective reprocessing capability, reducing the need for reanalysis when new targets arise.

Benefits and practical applications

The evaluated approach provides several practical advantages for routine pesticide residue laboratories:

• Enhanced selectivity and reduced false positives in complex or pigmented matrices due to high resolving power and accurate-mass discrimination of isobaric/coeluting interferences.
• Lower detection limits (≤0.5 µg/kg for most analytes), permitting monitoring below common regulatory thresholds and supporting confirmatory analysis at trace levels.
• Single-acquisition workflows that combine quantitation and screening improve throughput and enable retrospective review for additional analytes without re-running samples.
• Robust ion source design (NeverVent AEI) improves uptime and supports high sample throughput for a faster return on investment.

Future trends and potential applications

High-resolution full-scan GC–Orbitrap technology is well-positioned to expand its role in food safety and environmental monitoring. Anticipated directions include:

• Broader implementation of retrospective screening databases and non-targeted discovery workflows to detect emerging contaminants alongside routine targets.
• Further optimization of ion sources and chromatographic interfacing to push detection limits and improve robustness for increasingly complex matrices.
• Integration with advanced data-processing platforms and machine-learning approaches to streamline compound identification and reduce manual review effort.
• Increased adoption in regulatory and commercial laboratories as HRAM methods become standardized and validated across multi-laboratory ring trials.

Conclusion

The Orbitrap Exploris GC S coupled with the NeverVent AEI source and an FS-HRAM workflow demonstrated compliant, high-sensitivity, and highly selective performance for multiresidue pesticide analysis in a challenging spinach matrix. Key performance highlights include IDLs at or below 0.5 µg/kg for most analytes, excellent linearity (0.5–200 µg/kg, R² > 0.993), consistent mass accuracy (≈3 ppm or better), and recoveries of 96–104%. The method supports simultaneous quantitation and retrospective screening, making it a practical solution for routine food-safety laboratories facing complex matrices.

Reference

1. SANTE/11312/2021 v2026. Analytical quality control and method validation procedures for pesticide residues analysis in food and feed. Implemented 01/01/2026.