DEVELOPING A ROBUST LC-MS/MS METHOD FOR THE DETERMINATION OF ANIONIC POLAR PESTICIDES IN A RANGE OF FOODSTUFFS WITHOUT DERIVATIZATION

Importance of the Topic

Concerns about glyphosate and other polar anionic pesticides have increased global demand for effective surveillance in food safety. Traditional reversed phase columns lack sufficient retention for such compounds, prompting the development of direct analysis methods without derivatization or ion pairing.

Study Objectives and Overview

This work aimed to create a robust LC-MS/MS protocol capable of determining a wide range of polar anionic pesticides and metabolites in various food matrices. Key goals included enhancing chromatographic retention, achieving reliable separation of critical pairs, minimizing matrix effects, and simplifying sample preparation.

Methodology

Samples from retail sources (tomato, wheat flour, tea) were homogenized and extracted following a modified QuPPe procedure using acidified acetonitrile. Two chromatographic methods (A and B) were optimized on a Torus DEA stationary phase. Method A employed a buffered formic acid mobile phase, while Method B used a formic acid only mobile phase to boost sensitivity. Method performance was assessed by retention factor (t0 multiples), retention time stability, accuracy and precision at 5 and 20 ppb spike levels, and linearity across 0.002 to 0.2 mg/kg.

Instrumentation

The analysis utilized a UPLC-MS/MS platform fitted with a Torus DEA (ethylene bridged hybrid with diethylamine ligands) column. This configuration combines hydrophilic surface properties with weak anion exchange interactions, promoting strong retention and clean peak shapes for highly polar anions.

Key Results and Discussion

• Retention: All targets eluted at least 3.5 times the column dead volume, meeting guideline requirements.
• Separation: Baseline resolution achieved for critical isobaric pairs including AMPA vs phosphonic acid and fosetyl, preventing false positives.
• Stability: Retention time shifts remained below 0.1 min over extended runs, demonstrating robustness.
• Accuracy and Precision: For tomato and wheat flour at 5 and 20 ppb, trueness ranged 70–120% with RSD below 10% (n=15).
• Linearity: Matrix matched calibration curves showed R2 > 0.995 with residuals under 20%.
• Matrix Effects: RADAR full-scan monitoring highlighted matrix complexity and supported potential cleanup strategies to reduce ion suppression.

Benefits and Practical Applications

This single-method approach allows simultaneous analysis of multiple polar pesticides, avoiding time-consuming derivatization and multiple single-residue assays. It delivers reliable detection at sub-MRL levels, simplifies laboratory workflows, and enhances confidence in regulatory compliance testing.

Future Trends and Opportunities

• Expanding analyte scope to include chlorate, perchlorate and other emerging polar contaminants.
• Integration of high-resolution full scan MS for non-targeted screening and retrospective data analysis.
• Automation of sample cleanup to further reduce matrix effects and increase throughput.
• Development of universal extraction protocols to cover broader compound classes in a single workflow.

Conclusion

The Torus DEA UPLC-MS/MS method provides a reliable, sensitive, and streamlined solution for determining polar anionic pesticides in diverse food matrices. Its robust retention, separation and detection capabilities support effective food safety monitoring without derivatization or ion pairing.

References

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