ROUTINE DETERMINATION OF HIGHLY POLAR CATIONIC PESTICIDES AND PLANT GROWTH REGULATORS BY LC-MS/MS

Importance of the Topic

Highly polar cationic pesticides and plant growth regulators pose analytical challenges due to their solubility and matrix interferences. Reliable detection of these compounds in food is crucial for compliance with regulatory limits and ensuring consumer safety.

Objectives and Study Overview

This study evaluates a streamlined workflow based on the QuPPe sample extraction combined with UPLC-MS/MS to quantify multiple polar cationic pesticides and growth regulators in fruit, vegetables, and cereals.

Methodology and Instrumentation

• Sample Preparation: Homogenization of apples, cucumbers, potatoes, and wheat flour; water content adjustment; methanol extraction with formic acid.
• Extraction Protocol: QuPPe method featuring freeze-out at -80°C and centrifugation followed by PTFE filtration.
• Chromatographic Conditions: ACQUITY UPLC I-Class-FL system, BEH Amide column (2.1×50 mm, 1.7 µm), mobile phases of ammonium formate buffer (pH 2.95) and acetonitrile, 40°C column temperature.
• Mass Spectrometry: Xevo TQ-S micro in ESI+ mode (ESI- for hydrazide), MRM acquisition with two transitions per analyte, capillary voltage 1.00 kV, desolvation temperature 600°C.

Main Results and Discussion

• Linearity and sensitivity: Calibration achieved R² ≥ 0.995 using 1/x weighting from 0.002 to 0.2 mg/kg (0.004–0.4 mg/kg in flour); LOQs down to 0.01 mg/kg.
• Precision and trueness: Recoveries of 92–108% across commodities, except 60–67% for difenzoquat in cucumber due to filter incompatibility; RSDs ≤ 12%.
• Retention time stability: Over 200 injections in flour matrix showed shifts < 0.01 minutes and RSD < 0.3%.
• QC validation: FAPAS flour sample results within ±20% of assigned values across two batches one month apart.
• Throughput: Ten‐minute run time supports high sample throughput for routine monitoring.

Benefits and Practical Applications

• Single‐step extraction and analysis reduces labor and potential errors compared to derivatization or ion‐pair methods.
• Compliance with SANTE guidelines ensures regulatory acceptance for routine monitoring.
• Applicable to diverse matrices, including high‐water and high‐starch commodities.

Future Trends and Potential Uses

Anticipated developments include integration of automated QuPPe workflows, expansion of target lists to emerging polar analytes, and coupling with high‐resolution mass spectrometry for non‐target screening and metabolite profiling.

Conclusion

The combined QuPPe extraction and UPLC‐MS/MS method provides a robust, sensitive, and rapid approach for quantifying polar cationic pesticides and plant growth regulators in food matrices, facilitating regulatory compliance and ensuring food safety.