Non-targeted Screening and Accurate Mass Confirmation of 510 Pesticides on the High Resolution Exactive Benchtop LC/MS Orbitrap Mass Spectrometer

Significance of the Topic

As global food trade expands, regulatory agencies around the world are enforcing stricter maximum residue limits for pesticides to protect public health. Traditional gas chromatography methods face challenges with polar or thermally labile compounds. High resolution LC–MS platforms offer the sensitivity, speed and mass accuracy needed for high-throughput screening of hundreds of pesticides at trace levels.

Objectives and Study Overview

This study demonstrates non-targeted and targeted screening of 510 multi-class pesticides in food matrices using a benchtop high resolution Exactive Orbitrap LC–MS system. The aim was to achieve rapid separation, sensitive detection and accurate mass confirmation at or below regulatory default limits (10 ppb).

Methodology and Instrumentation

The analytical workflow combined efficient sample preparation and state-of-the-art instrumentation:

• Sample preparation: Modified QuEChERS extraction of pesticides from spinach with isotopically labeled internal standard
• Standard solutions: 3 mg/L stock of 510 pesticides; calibration range 1 – 250 ppb in acetonitrile/water
• Liquid chromatography: Thermo Scientific Accela U-HPLC with Hypersil GOLD aQ C18 column, water and methanol mobile phases containing formic acid and ammonium formate, 12 min gradient at 300 µL/min
• Mass spectrometry: Thermo Scientific Exactive Orbitrap, full scan positive/negative mode m/z 100 – 1500, resolution 50 000, AGC target 1e6, heated electrospray ionization
• Data processing: Xcalibur software for acquisition; Pathfinder for automated screening and mass confirmation

Key Results and Discussion

• Rapid separation and detection of 510 pesticides within a 12 min LC run
• Mass accuracy below 5 ppm for most compounds enabled clear differentiation of isobaric pairs
• Excellent linearity (correlation coefficients > 0.99) over 1 – 250 ppb
• Limits of quantitation for 499 pesticides at or below 10 ppb; full compliance with EU and Japanese default limits
• Spiked spinach matrix analysis yielded method detection limits below 1 ppb and LOQs of 0.2 – 0.9 ppb for representative compounds
• Full-scan Orbitrap MS screening eliminates the need for compound-specific MS/MS method optimization

Benefits and Practical Applications

• High throughput and cost-effectiveness for routine monitoring laboratories
• Simultaneous targeted and non-targeted pesticide screening using a single full-scan approach
• Accurate mass confirmation for regulatory compliance at trace levels
• Robust performance in complex food matrices without extensive method development

Future Trends and Potential Applications

Advances in high resolution mass spectrometry and data analytics will further streamline non-targeted screening workflows. Integration with machine learning, miniaturized sample preparation, and expansion to other contaminant classes will enhance monitoring capabilities. Portable high resolution MS and cloud-based spectral libraries are poised to accelerate on-site testing and real-time regulatory decision-making.

Conclusion

The Thermo Scientific Exactive benchtop Orbitrap LC–MS platform enables rapid, sensitive and accurate multiresidue pesticide analysis. The demonstrated method achieves high resolution separation, low ppb detection limits and robust mass confirmation of over 500 pesticides in under 12 minutes, making it ideal for routine compliance screening in regulatory and quality control laboratories.

References

1. US EPA Pesticide Tolerance Reassessment — Federal Food Quality Protection Act accomplishments
2. National Standard GB 2763-2005, Maximum residue limits for pesticides in food, People’s Republic of China
3. Japan Positive List System for Agricultural Chemicals in Foods
4. EU Regulation 396/2005 on maximum residue levels of pesticides
5. EU Directive 91/414/EEC pesticide approval and review
6. Thermo Scientific Orbitrap Technology Application Note 30163
7. Thermo Scientific Exactive Benchtop LC/MS Application Note 30162
8. AOAC Official Method 2007.01 QuEChERS pesticide residues in foods
9. US EPA Method Detection Limit procedure 40 CFR Part 136 Appendix B