LAPRW 2017: An Assessment of GC Orbitrap MS Technology for the Routine Screening and Quantification of Pesticide Residues in Food

Importance of the topic

The reliable detection and quantification of pesticide residues in food matrices is essential for consumer safety, regulatory compliance and trade. High-resolution mass spectrometry (HR-MS) coupled with gas chromatography (GC) offers a full-scan capability that overcomes the target-only limitations of triple quadrupole systems, while delivering the selectivity and quantitative performance required by international guidelines.

Objectives and study overview

This study assessed the performance of the Thermo Scientific Exactive GC Orbitrap GC-MS system for routine screening and quantification of 51 pesticides in tomato, leek and orange matrices. The work was conducted according to SANTE/11945/2015 guidelines, evaluating limits of detection, identification, mass accuracy, repeatability and robustness over six orders of magnitude in concentration.

Methodology and instrumentation used

Sample preparation followed a buffered QuEChERS extraction protocol:

• Tomato, leek and orange homogenates extracted with acetate-buffered salts.
• Centrifugation and cleanup using magnesium sulfate and PSA.
• Final ethyl acetate extracts at 1 g/mL used for analysis.

GC parameters:

• Thermo Trace 1310 GC with single taper LinerGOLD inlet at 280 °C.
• Oven ramp from 40 °C to 300 °C in three segments.
• Helium carrier gas at 1.2 mL/min.

MS conditions:

• Exactive Orbitrap analyzer with EI at 70 eV.
• Full-scan 50–550 Da at 60 000 FWHM resolving power.
• Mass accuracy sub-0.6 ppm RMS using lockmass calibration.
• Data processed with TraceFinder software for automated identification and quantification.

Main results and discussion

High-quality chromatographic separation was observed for all matrix types. Key findings include:

• Limits of identification (LOI) ≤5 µg/kg for all compounds (except known-chlorothalonil degradation in leek).
• LODs ≤1 µg/kg for over 90% of analytes.
• Mass accuracy consistently <1 ppm across 0.1–10 000 ng/mL concentrations.
• Repeatability RSD <10% at 10 µg/kg in all matrices (n=10) and stable performance over 100 injections (66 h continuous analysis) with RSD ≤5.3%.
• 99.3% pesticide/matrix combinations detected below maximum residue limits with R² >0.99 linearity.

Benefits and practical applications

The Exactive GC Orbitrap system delivers comprehensive screening capability without sacrificing quantitative reliability. Its full-scan HR-MS approach offers:

• Expanded scope for non-target or unexpected analytes.
• Robust performance for high-throughput routine laboratories.
• Enhanced confidence in compound confirmation via accurate mass and isotopic patterns.

Future trends and potential applications

Advances in HR-MS instrumentation and data processing are expected to further improve sensitivity, speed and data mining capabilities. Future developments may include:

• Integration of retrospective non-target screening workflows.
• Machine-learning algorithms for automated anomaly detection.
• Miniaturized and field-deployable GC-HR-MS systems for on-site testing.

Conclusion

The Thermo Scientific Exactive GC Orbitrap GC-MS, combined with TraceFinder software, meets SANTE guidelines for pesticide residue analysis in fruits and vegetables. The system demonstrated exceptional mass accuracy, sensitivity, linearity and repeatability, enabling confident routine screening and quantification.

References

• SANTE/11945/2015. Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed.
• Belmonte Valles N., Retamal M., Martinez-Uroz M.A., Mezcua M., Fernandez-Alba A.R., de Kok A. (2012) Determination of chlorothalonil in difficult matrices. Analyst, 137, 2513-2520.