Achieving method reliability in the routine determination of anionic polar pesticides in food

Importance of the Topic

Routine monitoring of anionic, highly polar pesticides has become critical due to safety concerns over glyphosate residues in food. Standard reversed-phase methods fail to retain these low-molecular-weight compounds, driving the need for robust, simplified workflows that avoid derivatization and ion pairing.

Objectives and Study Overview

This study presents the development of a single UPLC-MS/MS method for the reliable analysis of 13 anionic polar pesticides and metabolites in food matrices. The approach extends beyond glyphosate, glufosinate and AMPA to include chlorate, perchlorate and other challenging analytes within one routine assay.

Methodology and Instrumentation

Sample Preparation

• Homogenization of retail food samples followed by QuPPe acidified methanol extraction
• Comparison with generic aqueous extraction methods

Chromatography and Detection

• Waters Anionic Polar Pesticide column 186009287 on a standard UPLC-MS/MS system
• Method A with buffered formic acid mobile phase for broad coverage including chlorate and perchlorate
• Method B with formic acid mobile phase for enhanced sensitivity
• RADAR full-scan acquisition to monitor ion suppression and support potential clean-up decisions

Used Instrumentation

Waters Anionic Polar Pesticide column 186009287, UPLC-MS/MS platform with ESI source configured for multiple reaction monitoring.

Main Results and Discussion

The optimized methods achieved:

• Retention factors exceeding three times the void volume, ensuring all analytes elute well after t0
• Retention time stability within ±0.1 min across tomato, cucumber, and wheat flour extracts
• Baseline separation of isobaric pairs such as phosphonic acid vs fosetyl-aluminium and n-acetyl-AMPA vs AMPA to prevent false positives
• Detection limits in the low ppb range, surpassing current MRL requirements
• Recovery between 70 and 120% with RSD < 5% at 0.01 mg/kg spike levels

Benefits and Practical Applications

The single-injection workflow avoids multiple residue protocols and derivatization steps, increasing laboratory throughput and simplifying trace-level screening of polar pesticides in diverse food commodities.

Future Trends and Applications

Potential developments include:

• Expansion of analyte scope via high-resolution full-scan acquisition
• Integration of automated sample clean-up to further reduce matrix effects
• Application of machine learning for data analysis and anomaly detection
• Adaptation for regulatory compliance across global monitoring networks

Conclusion

A robust, user-friendly UPLC-MS/MS method has been established for routine determination of anionic polar pesticides. It delivers reliable, sensitive detection in low-ppb levels and fully meets or exceeds current regulatory standards.

References

1. EU SANTE 11813/2017 Guidance Document on Analytical Quality Control and Method Validation Procedures for Pesticide Residues.
2. European Commission QuPPe Method 2019.
3. Chamkasem N, Harmon T, Anal Bioanal Chem. 2016, 408(18):4995–5004.