Implementing GC-HRAM MS for More Efficient and Effective Routine Pesticide Residues Analysis

Significance of the Topic

Routine analysis of pesticide residues in food and feed demands detection of hundreds of compounds at trace levels (10 ng/g and lower) across complex matrices. Traditional nominal-mass GC-MS and targeted MS/MS methods face limitations in selectivity, flexibility, and the capacity for retrospective screening. High-resolution accurate-mass GC-MS (GC-HRAM-MS) addresses these challenges by combining full-scan data acquisition with enhanced mass accuracy and resolving power.

Objectives and Overview of the Study

This work evaluates the Thermo Scientific™ Exactive™ GC Orbitrap™ MS and Q Exactive™ GC Orbitrap™ GC-MS/MS systems for routine, non-targeted and targeted pesticide residue analysis. Key goals include demonstrating improved selectivity over nominal-mass methods, establishing optimal mass resolution and extraction windows, and validating quantitative and qualitative performance in various matrices.

Methodology

Full-scan GC analyses were performed using electron ionization and optional chemical ionization sources. Analysts tested resolving powers of 15 000, 30 000, 60 000 and 120 000 (FWHM @ m/z 200) to assess mass accuracy and selectivity. Mass extraction windows (MEWs) of ±0.5 Da, ±25 ppm and ±5 ppm were compared using chlorpropham in leek matrix. Validation included matrix-matched calibration in leek, orange and tomato at 0.5–250 µg/mL, SANTE guideline compliance for identification, and application to cereal and feed extracts without solvent exchange.

Instrumentation

• Exactive GC Orbitrap GC-MS system: EI source, C-trap, Orbitrap analyzer, resolving power up to 60 000
• Q Exactive GC Orbitrap GC-MS/MS: includes collision cell for MS/MS, resolving power up to 120 000
• Injection modes: hot splitless for ≤1 µL; PTV with sintered liner for larger volumes
• Software: Thermo Scientific™ TraceFinder™ with accurate-mass library and deconvolution plug-in for quantitation and screening

Main Results and Discussion

High resolving power (≥60 000) enabled mass accuracy within 5 ppm for 100% of pesticide/matrix combinations, matching or exceeding selectivity of triple-quadrupole MS/MS. Narrow MEWs (±5 ppm) eliminated matrix interference effectively. In leek, orange and tomato, limits of detection and identification were 0.5–10 ng/g for most compounds; retention time stability was within ±0.1 min. Application to cereals and feed showed average recoveries of 71–120% and repeatability ≤20% for 91 of 97 analytes, with excellent selectivity (no signals above 30% of reporting limits in blank samples). Qualitative screening workflows—spectral library matching and RT plus exact-mass extraction—demonstrated detection rates of ≥86% for 50 pesticides at 10 ng/g.

Benefits and Practical Applications

GC-HRAM-MS offers combined non-targeted full-scan acquisition and targeted quantitation within a single run, reducing method development effort and enabling retrospective data interrogation for emerging contaminants. High resolving power and mass accuracy provide superior selectivity in complex matrices without sensitivity loss, supporting regulatory compliance and broad-scope screening in QA/QC, research and industrial laboratories.

Future Trends and Potential Applications

• Integration of larger accurate-mass libraries and automated deconvolution for faster qualitative screening
• Hybrid workflows adding SIM events to full-scan methods for ultra-trace analytes
• Development of standardized high-throughput sample preparation and data processing pipelines
• Expansion to other small-molecule residues and metabolites in food safety and environmental monitoring

Conclusion

The Exactive GC Orbitrap MS platform delivers equal or improved selectivity and sensitivity compared to GC-MS/MS, with the added advantage of full-scan, high-resolution data for flexible, retrospective pesticide residue analysis. It meets stringent regulatory requirements while simplifying routine workflows and expanding screening capabilities.

Reference

1. The Pesticide Manual, 17th Edition, J.A. Turner, British Crop Production Council, 2015
2. European Commission SANTE/11945/2015, Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticides Residues Analysis in Food and Feed, 2017