Screening of Contaminants in Food and Natural Products by GC/Q-TOF with an Accurate Mass Pesticides and Environmental Pollutants Library

Significance of the Topic

Comprehensive screening of pesticides and environmental pollutants in food and natural products is vital to safeguard consumer health and comply with strict regulatory standards. High-resolution mass spectrometry, particularly GC/Q-TOF, enables full spectrum data acquisition that captures both targeted analytes and unexpected contaminants in a single run.

Objectives and Study Overview

This work presents the development and application of an accurate mass pesticides and environmental pollutants library tailored for GC/Q-TOF screening. The library contains retention times for 20- and 40-minute methods and high-resolution mass spectra for over 1000 compounds. The study demonstrates:

• Targeted screening in fruits and vegetables
• Suspect screening in essential oils
• Approaches for unknown identification through low-energy EI and MS/MS

Methodology and Instrumentation

A GC/Q-TOF system (Agilent 7250) was configured with a mid-column backflush to improve cycle time and prevent late-eluting contaminants from entering the source. Key operational settings included:

• HP-5MS UI capillary columns in series with retention time locking
• Cold splitless injection of 2 µL and helium carrier gas at 1 mL/min
• Oven ramp from 60 °C to 310 °C, followed by backflush at 50 psi
• Electron ionization at 70 eV and low-energy EI at 15 eV
• Spectral acquisition at 45–650 m/z at 5 spectra/sec

Sample preparation employed QuEChERS extraction with dispersive SPE cleanup for solid food matrices and dilution in ethyl acetate for essential oils.

Main Results and Discussion

Targeted screening in non-organic apple, avocado, broccoli and orange revealed up to 21 contaminants in single samples. Broccoli, as a challenging matrix, yielded 19 hits including pesticides (azoxystrobin, boscalid, dimethomorph) and pollutants (phenanthrene, p,p′-DDE) with retention time deviations under 0.05 min, coelution scores above 80 %, and mass errors below 3 ppm. Suspect screening of essential oils identified 17 compounds in orange oil, including phthalates and chlorinated aromatics. Unknown features discovered by untargeted analysis were elucidated using low-energy EI to confirm molecular ions and accurate mass MS/MS for formula confirmation, leading to identification of degradation products such as 2,4,5-trichloroisophthalonitrile.

Benefits and Practical Applications

The integrated library and GC/Q-TOF workflow offers:

• Broad contaminant coverage beyond conventional targets
• High confidence identifications through retention time locking and sub-5 ppm mass accuracy
• Rapid method cycles enabled by backflushing
• Capability to discover and elucidate unknowns

Future Trends and Applications

Advances likely to further enhance screening include:

• Expansion of accurate mass libraries to cover emerging contaminants
• Integration of machine learning for automated peak annotation
• Miniaturized GC/Q-TOF systems for in-field analysis
• Enhanced software workflows for multi-vendor spectral libraries

Conclusion

The updated accurate mass pesticides and environmental pollutants library, combined with high-resolution GC/Q-TOF, enables comprehensive and confident screening of diverse food and natural product matrices. The approach balances sensitivity, speed, and broad scope, while low-energy EI and accurate mass MS/MS facilitate elucidation of unexpected contaminants.

Reference

1. Chen K., Sanders J. Agilent Technologies Application Brief, 5991-8170EN (2017)
2. Chen K., Nieto S., Stevens J. Agilent Technologies Application Note, 5991-7691EN (2016)