Highly Polar Pesticide Multi-Residue Analysis in Food Safety by LC-MS/MS

Importance of the Topic

The increasing adoption of highly polar pesticides in agriculture has driven demand for analytical methods capable of monitoring a broad spectrum of residues in food matrices. Regulatory bodies enforce maximum residue limits (MRLs) to ensure consumer safety, and laboratories require rapid, sensitive workflows to support high sample throughput. Conventional single-residue or small group-specific assays prolong analysis time and increase cost, highlighting the need for multi-residue approaches that maintain performance across diverse chemical properties.

Objectives and Study Overview

This study aimed to develop and validate two multi-residue LC-MS/MS methods for the direct analysis of 17 challenging polar pesticides—such as glyphosate, glufosinate, diquat, paraquat, perchlorate and others—in food matrices without chemical derivatization. By employing a Shimadzu LCMS-8050 triple quadrupole system, the work sought to simplify sample preparation, reduce analysis time and achieve quantitation down to 0.01 mg/kg, below European Union MRLs for all target analytes.

Methodology and Instrumentation

Sample Preparation:

• Apple samples (10 g) homogenized with dry ice.
• Extraction with 1% formic acid in methanol (10 mL), followed by centrifugation.
• Plastic vials used to avoid adsorption of cationic herbicides onto glass.
• Calibration performed using matrix-matched standards from 0.005 to 0.2 mg/kg, with deuterated internal standards.

Instrumentation

• LC: Shimadzu Nexera UHPLC.
• MS: Shimadzu LCMS-8050 triple quadrupole with heated electrospray ionization and fast polarity switching.
• Columns:
  
  • ZIC-HILIC (100 × 2.1 mm, 3.5 µm) for Method 1.
  • Porous graphitic carbon Hypercarb PGC (100 × 2.1 mm, 5 µm) for Method 2.
• Mobile Phases:
  
  • Method 1: 20 mM ammonium formate/0.3% formic acid in water (A) and acetonitrile (B).
  • Method 2: 1% acetic acid in water (A) and methanol (B).
• Gradient times, flow rates and temperature optimized for each column.

Main Results and Discussion

Both methods successfully separated and detected all 17 analytes at 0.01 mg/kg levels. Calibration curves exhibited excellent linearity (R² > 0.9975) across 0.005–0.2 mg/kg, using 1/C weighting and internal standard correction. Representative LOQs were well below EU MRLs (e.g., glyphosate 0.01 mg/kg, paraquat 0.02 mg/kg). High retention and peak shape stability were achieved: Method 1 effectively resolved quaternary ammonium herbicides and small molecules on a zwitterionic HILIC phase, while Method 2 provided robust retention of acidic and neutral analytes on PGC. The sensitivity gains permit sample extract dilution to mitigate matrix effects and extend column lifetime.

Benefits and Practical Applications

• Consolidation of multiple single-residue assays into two runs reduces instrument time and labor.
• Direct analysis without derivatization streamlines workflows and improves reproducibility.
• Sensitivity below MRLs ensures regulatory compliance across diverse food matrices.
• Use of internal standards compensates for matrix variability, enhancing quantitation accuracy.

Future Trends and Opportunities

• Integration with high-throughput sample preparation robotics for large-scale monitoring programs.
• Expansion to additional polar contaminants, including metabolites and degradation products.
• Implementation of fast scanning HRMS for non-targeted screening alongside targeted MRM workflows.
• Method adaptation to other food matrices and environmental samples for broader surveillance.

Conclusion

The two developed LC-MS/MS workflows achieve rapid, sensitive, and reliable quantitation of a wide range of highly polar pesticides without derivatization. By leveraging complementary HILIC and PGC separations on a single MS platform, laboratories can significantly improve throughput, reduce costs, and maintain the analytical rigor required for regulatory compliance in food safety.

References

1. European Union Reference Laboratory for Pesticides Requiring Single Residue Methods (EURL-SRM). Quick Method for the Analysis of Highly Polar Pesticides in Foods of Plant Origin (QuPPe-Method), Version 7, 2012.
2. European Commission Regulation (EC) No 396/2005 of the European Parliament and of the Council on Maximum Residue Levels of Pesticides in or on Food and Feed, Official Journal of the European Union L 70, 2005.