GC/Q-TOF Screening of Pesticides in Food

Significance of the Topic

The reliable detection and confirmation of pesticide residues in food is critical for protecting public health, ensuring regulatory compliance, and maintaining consumer confidence. High-resolution accurate mass gas chromatography–quadrupole time-of-flight (GC/Q-TOF) screening provides comprehensive spectral data for multiresidue analysis at low concentration levels, enabling both targeted and untargeted detection of known and unexpected contaminants.

Objectives and Study Overview

This work evaluates an integrated workflow for multiresidue pesticide screening in complex food matrices using the Agilent 7200 Series GC/Q-TOF system, Agilent MassHunter Qualitative Analysis Software, and the updated Agilent MassHunter GC/Q-TOF Pesticides Personal Compound Database and Library (PCDL). The study aims to demonstrate:

• Reliable identification of over 17 representative pesticides at 10 ng/mL equivalent in blended food extracts.
• Verification of compound identity using coelution scoring, mass error assessment, and fragment ion ratio matching.
• Detection and confirmation of unexpected pesticide impurities.
• Customization and expansion of the PCDL with new analyte spectra for retrospective screening.

Methodology and Instrumentation

Food samples were extracted by a QuEChERS-based procedure. Analysis was performed on an Agilent 7890B GC with midcolumn backflush coupled to an Agilent 7200B Q-TOF operated in electron ionization full-spectrum mode. Two HP-5ms UI columns (15 m × 0.25 mm, 0.25 µm) with retention time locking to chlorpyrifos-methyl were used. The Q-TOF acquired spectra at 5 Hz over m/z 45–550, with high-resolution accurate mass data processed in centroid mode. Suspect screening leveraged the MassHunter Find by Fragments algorithm and the updated PCDL containing over 850 pesticide entries with reference retention times and accurate mass spectra.

Used Instrumentation

• Agilent 7890B Gas Chromatograph with midcolumn backflush configuration
• Agilent 7200B Q-TOF Mass Spectrometer, EI ionization, 4 GHz acquisition
• Agilent MassHunter Qualitative Analysis Software with Find by Fragments workflow
• Agilent GC/Q-TOF Pesticides Personal Compound Database and Library (PCDL)

Main Results and Discussion

• Seventeen pesticides spiked at 10 ng/mL in blended food extracts were identified in six replicates with coelution scores ≥70, retention time deviations <0.03 min, and mass errors <5 ppm.
• Atrazine was verified with a fragment ratio score >99, demonstrating excellent matching of ion abundance ratios between sample spectra and the PCDL library.
• Unexpected o,p′-DDE was detected at trace levels in the food extract, confirmed by coelution, fragment ratio (>80), and <5 ppm mass errors. Comparison with spiked standard mixtures revealed it as an impurity in the pesticide pull-down standard.
• The workflow supports retrospective analysis: new pesticide spectra can be curated and added to a custom PCDL via automatic formula annotation and subformula verification, enhancing surveillance flexibility.

Benefits and Practical Applications

• High-confidence multiresidue screening with both targeted and untargeted capabilities.
• Rapid verification criteria based on coelution, fragment ratio scoring, and mass accuracy.
• Expandable compound library for evolving regulatory or research needs.
• Retrospective data mining for emerging analytes without reanalysis.

Future Trends and Applications

The integration of GC/Q-TOF screening with advanced software and machine-learning algorithms will further streamline suspect and non-targeted pesticide monitoring. Expansion of compound libraries through community sharing and automatic spectral curation will support broader coverage. Application to additional food matrices, environmental samples, and high-throughput regulatory testing is anticipated, alongside tighter coupling with quantitative workflows for confirmatory reporting.

Conclusion

The Agilent 7200 Series GC/Q-TOF platform coupled with MassHunter software and a customizable PCDL offers a robust solution for multiresidue pesticide screening in food. It delivers low-level detection, high-resolution confirmation, and flexible library management to meet current and future food safety challenges.

References

1. Belmonte-Valles N., et al., Anal. Methods 7, 2162–2171 (2015).
2. Wylie P.L., Stevens J., Nieto S., Agilent Technologies Application Note 5991-5633EN (2015).
3. Fernández-Alba A.R., Uclés S., Riener J., Agilent Technologies Application Note 5991-5894EN (2015).