GC/Q-TOF MS Surveillance of Pesticides in Food

Significance of the Topic

Ensuring food safety through monitoring pesticide residues is critical to protect public health and comply with regulatory maximum residue limits. High-resolution accurate mass GC/Q-TOF MS offers combined quantitative and qualitative screening in a single injection, increasing laboratory efficiency and expanding the scope of detectable compounds.

Study Objectives and Overview

This application note presents a workflow integrating the Agilent 7200 Series GC/Q-TOF system, MassHunter software, and the updated Pesticides Personal Compound Database and Library (PCDL) to:

• Perform quantitative screening using calibration standards for selected pesticides.
• Enable qualitative (suspect) screening against the PCDL for compounds without standards.
• Validate performance across diverse food matrices including fruits, vegetables, and salmon.

Methodology and Instrumentation

Sample Preparation and Extraction:
A range of organic food samples (apple, avocado, cucumber, peach, tomato, salmon) were processed using QuEChERS protocols (EN 15662, AOAC 2007.1) with clean-up steps for high-lipid matrices.

Instrumentation:

• GC: Agilent 7890B with midcolumn backflush, dual HP-5ms UI columns (15 m × 0.25 mm, 0.25 μm).
• Injection: Splitless, cold MMI liner, retention time locking to chlorpyrifos-methyl (9.143 min).
• MS: Agilent 7200B Q-TOF, EI mode, mass range 45–550 m/z, spectral rate 5 Hz, 4 GHz high-resolution acquisition.
• Software: MassHunter Qualitative Analysis B.08 and Quantitative Analysis B.08 with Pesticides PCDL (850+ compounds).

Main Results and Discussion

Quantitative Performance:

• Linear calibration (5–200 ng/mL) with R² ≥ 0.99 for over 105 pesticides in peach and avocado.
• Fast two-level screening at 5 and 20 ng/mL achieved ±20 % accuracy for more than 117 pesticides at a 10 ng/mL spike level across all matrices.
• Retention time and response repeatability demonstrated low RSD (< 10 %) over replicate injections and long sequences (36 injections).

Qualitative Screening:

• Automated extraction of up to six ions per compound, with coelution score ≥ 70 and S/N ≥ 3, resulted in identification of 116–119 pesticides at 10 ng/mL.
• High mass accuracy (< 5 ppm for most compounds) and stable ion ratios (< 30 % deviation) supported confident identification.

Practical Benefits and Applications

The combined GC/Q-TOF workflow allows laboratories to:

• Flexibly select compounds for quantitative calibration while screening a broader suspect list qualitatively.
• Reduce calibration workload and costs for low-frequency contaminants.
• Leverage full-scan accurate mass data for retrospective analysis and expanded scope without method re-development.

Future Trends and Opportunities

Advances are expected in:

• Expansion of high-resolution spectral libraries covering emerging and transformation products.
• Integration with automated data analytics and machine learning for non-targeted screening.
• Higher throughput GC configurations and faster scan rates to accommodate larger sample batches.

Conclusion

This workflow demonstrates that high-resolution accurate mass GC/Q-TOF combined with specialized software and libraries provides a robust, efficient solution for quantitative and qualitative pesticide screening in complex food matrices, ensuring high confidence results and operational flexibility.

Reference

1. SANTE/11945/2015. Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed. European Commission, 2015.
2. Wylie P.L., Stevens J., Nieto S. Screening for More Than 740 Pesticide Residues in Food Using an Agilent GC/Q-TOF and an Exact Mass Pesticide Library. Agilent Technologies Application Note 5991-5633EN, 2015.
3. Fernández-Alba A.R., Uclés S., Riener J. Screening for Hundreds of Pesticide Residues Using a GC/Q-TOF with an Exact Mass Pesticide Database in Food. Agilent Technologies Application Note 5991-5894EN, 2015.
4. Chen K., Stevens J., Nieto S. GC/Q-TOF Screening of Pesticides in Food - Searching and Verification using Agilent MassHunter GC/Q-TOF Pesticide Personal Compound Database and Library. Agilent Technologies Application Note 5991-6884EN, 2016.
5. Lehotay S.J., Sapozhnikova Y., Mol H.G.J. Current issues involving screening and identification of chemical contaminants in foods by mass spectrometry. Trends Anal. Chem. 60, 62-75, 2015.