A Comparison of IC-MS/MS and LC-MS/MS Techniques for the Multi-Residue Analysis of Polar Pesticides and Metabolites in Food

Importance of the Topic

The reliable determination of highly polar pesticide residues and their metabolites in food matrices is a critical challenge in food safety and regulatory monitoring. Conventional reversed phase liquid chromatography often fails to retain these analytes effectively, leading to poor sensitivity and reproducibility. Advanced MS based workflows provide improved retention, peak shape, and quantitative performance for these difficult compounds.

Study Objectives and Overview

This study evaluates and compares three analytical approaches for the simultaneous analysis of multiple polar pesticides and their metabolites in diverse food matrices. Methods under investigation include:

• LC-MS/MS with a porous graphitic carbon column
• LC-MS/MS with a mixed-mode hydrophilic interaction/ion exchange column
• IC-MS/MS with a high capacity ion exchange column and post column eluent suppression

Evaluation criteria comprised recovery, precision, accuracy, retention time stability, peak shape, and sensitivity in leek, fruit based baby food, and turmeric powder spiked at 10 and 50 ng/g.

Methodology and Instrumentation

Sample preparation was based on a modified Quick Polar Pesticide extraction protocol, including methanol extraction, cold precipitation, centrifugation, solid phase clean-up with OnGuard II RP cartridges, and 0.2 μm filtration. Turmeric samples underwent an additional Hypercarb cartridge cleanup prior to analysis.

Used Instrumentation

• Vanquish Flex UHPLC for LC separations
  • Porous graphitic carbon column Hypercarb 100×2.1 mm, 5 μm with acetic acid in water and methanol gradient
  • Mixed-mode Raptor X column with formic acid in water and acetonitrile gradient
• Dionex Integrion HPIC system
  • IonPac AS19 guard and analytical columns, electrolytic potassium hydroxide eluent generation, suppressed conductivity detection
• TSQ Altis triple quadrupole mass spectrometer in negative SRM mode for all methods

Main Results and Discussion

Key findings from comparative performance:

• IC-MS/MS delivered superior precision and accuracy with %RSD values below 3, excellent retention time stability, and sharp peak shapes across all matrices.
• Mixed-mode LC-MS/MS showed robust retention and good peak quality for most analytes but failed to retain N-acetyl glyphosate.
• PGC LC-MS/MS achieved universal retention of polar analytes after extensive column conditioning but exhibited higher retention time variability.
• Complex botanical matrices such as turmeric and ginger induced significant ion suppression, highlighting the need for enhanced sample cleanup.

Benefits and Practical Applications

• Streamlined multi-residue workflows enabling simultaneous detection of anionic pesticides at low ng/g levels.
• Improved quantitative reliability for regulatory food safety testing and quality control laboratories.
• Reduced analysis time by combining high-resolution separation with sensitive mass spectrometric detection.

Future Trends and Potential Applications

Anticipated developments include:

• Innovations in sample preparation to minimize matrix effects in complex botanical and food samples.
• Novel stationary phases and on-line cleanup strategies for universal retention of polar compounds.
• Broader integration of IC-MS/MS in routine laboratory workflows for comprehensive pesticide residue monitoring.
• Advanced data processing and artificial intelligence tools for improved peak identification and quantitation.

Conclusion

The comparative evaluation demonstrates that IC-MS/MS provides the most reliable performance for polar pesticide analysis in diverse food matrices, outperforming both porous graphitic carbon and mixed-mode LC-MS/MS in precision, accuracy, and robustness. Mixed-mode LC-MS/MS offers practical robustness but cannot detect certain metabolites, while PGC LC-MS/MS requires extensive conditioning. Internal standard calibration and improved cleanup protocols are recommended to further enhance method performance.

Reference

• Quick Polar Pesticides Method EURL for Pesticides https://www.eurl-pesticides.eu/docs/public/tmplt_article.asp?CntID=887&LabID=200&Lang=EN