High Efficiency, Broad Scope Screening of Pesticides Using Gas Chromatography High Resolution Orbitrap Mass Spectrometry

Importance of the Topic

Pesticide residues in food pose health and regulatory risks, requiring analytical methods capable of broad-scope, sensitive screening in complex matrices.

Objectives and Study Overview

This study evaluated the Thermo Scientific Q Exactive GC Orbitrap mass spectrometer combined with TraceFinder software for rapid, high-resolution screening of 55 GC-amenable pesticides in wheat, horse feed, and leek. Key goals included detection at or below maximum residue limits (MRLs), assessment of sensitivity, resolving power, and sample throughput.

Sample Preparation

Complex food matrices were prepared using an acidified QuEChERS extraction with acetonitrile and salt partitioning. Extracts were spiked with pesticide standards at 0.5–100 ng/g levels to evaluate method sensitivity in wheat, horse feed, and leek.

Used Instrumentation

• Q Exactive GC hybrid quadrupole-Orbitrap mass spectrometer
• TRACE 1310 gas chromatograph with TraceGOLD TG-5SilMS column (15 m × 0.25 mm × 0.25 μm)
• TriPlus RSH autosampler and PTV cold splitless inlet
• Electron ionization at 70 eV, full-scan 50–500 m/z, 60 000 FWHM resolving power

Data Processing

TraceFinder software performed full-scan screening against a database of 183 pesticides. Identification criteria included retention time ±20 s, mass accuracy ±2 ppm, isotopic pattern fit, and fragment ions. A traffic-light display enabled rapid review and retrospective data analysis.

Main Results and Discussion

• All 55 pesticides were detected at 10 ng/mL in three matrices; 53 were confirmed at <2.5 ng/mL in wheat, 47 at 0.5 ng/mL.
• GC analysis time was 17 minutes, supporting up to 84 injections per 24 hours, with ≥11 scans/peak for reliable integration.
• Resolving power of 60 000–120 000 FWHM provided sub-ppm mass accuracy and resolved matrix interferences; at 15 000–30 000 FWHM, coelutions led to false negatives (e.g., chlorpropham).
• Calibration showed linearity (R2 > 0.99) and residuals <25% across 0.5–50 ng/mL.

Benefits and Practical Applications

Full-scan high-resolution GC-MS extends screening scope without compound-specific optimization, reduces false positives through high mass accuracy, and enables targeted confirmatory analyses only for suspect samples, improving laboratory efficiency.

Future Trends and Opportunities

Adoption of high-resolution full-scan GC-MS in regulatory monitoring, expansion of spectral libraries, integration of machine learning for data interpretation, and coupling with novel ionization techniques promise further enhancements in contaminant screening.

Conclusion

The Q Exactive GC Orbitrap mass spectrometer paired with TraceFinder delivers rapid, sensitive, and selective broad-scope pesticide screening in complex food matrices, meeting regulatory requirements and maximizing laboratory throughput.

Reference

1. SANCO/12571/2013 Method validation and quality control procedures for pesticide residues in food and feed.
2. Kellmann M, Muenster H, Zomer P, Mol H (2009) Full Scan MS in Comprehensive Qualitative and Quantitative Residue Analysis in Food and Feed Matrices: How Much Resolving Power is Required? Journal of the American Society for Mass Spectrometry, 20, 1464–1476.
3. Thermo Scientific Application Note 10449: Fast screening, identification, and quantification of pesticide residues in baby food using GC Orbitrap MS technology.