Determination of Cationic Polar Pesticides and Plant Growth Regulators Using UPLC-MS/MS with the ACQUITY UPLC BEH Amide Column

Significance of the Topic

The analysis of highly polar cationic pesticides and plant growth regulators is critical for ensuring food safety and regulatory compliance with maximum residue limits (MRLs). Traditional multi-residue approaches often struggle with these compounds due to poor retention and matrix interferences. The Quick Polar Pesticides (QuPPe) extraction combined with UPLC-MS/MS offers a streamlined, sensitive solution capable of addressing these challenges across diverse food matrices.

Objectives and Study Overview

This study aimed to develop and validate a single-extraction, UPLC-MS/MS method using an ACQUITY UPLC BEH Amide column for determining multiple polar cationic pesticides and regulators in representative commodities: apple, cucumber, wheat flour, and potato. Performance was assessed against European Commission MRL requirements through recovery experiments, calibration linearity, retention time stability, and quality control samples.

Methodology

The QuPPe protocol was applied to homogenized samples, including a freezing step for flour, followed by filtration through 0.45 µm PTFE membranes. Spike recoveries at two levels (0.01 and 0.05 mg/kg, except maleic hydrazide at 0.5 and 1.5 mg/kg) were performed in quintuplicate. Matrix-matched brackets calibration covered 0.002–0.2 mg/kg (0.004–0.4 mg/kg for flour; 0.1–2 mg/kg for maleic hydrazide). Multireaction monitoring (MRM) transitions were optimized for quantification and confirmation, ensuring at least 12 data points per peak.

Instrumentation

• UPLC system: Waters ACQUITY UPLC I-Class with fixed-loop Sample Manager
• Column: ACQUITY UPLC BEH Amide, 1.7 µm, 2.1 × 100 mm at 40 °C
• Mass spectrometer: Xevo TQ-S micro, ESI+/ESI–
• Data software: MassLynx v4.2
• Filters and vials: 0.45 µm PTFE filters; polypropylene snap-neck vials with PTFE/silicone septa

Main Results and Discussion

Recovery (trueness) ranged from 92–108% for most analytes, with the exception of difenzoquat in cucumber (60–67%) traced to filter incompatibility. Precision (RSD) was ≤12%. Calibration curves exhibited R² ≥ 0.99 and residuals < 20%. Retention time stability across validation batches showed RSD < 3%, and after 200 continuous injections in flour, RSD remained < 0.3%. Matrix effects were effectively compensated by isotopically labeled standards; analytes without labels showed acceptable variability. Analysis of a FAPAS QC flour sample over two months yielded results within 20% of assigned values and repeatability < 2%.

Benefits and Practical Applications

• Single extraction and UPLC-MS/MS workflow suitable for a broad range of polar pesticides and regulators
• Meets SANTE guidelines for selectivity, retention, and sensitivity down to 0.01 mg/kg
• Short runtime (10 min) and minimal sample cleanup enhance laboratory throughput
• Robust performance across high-water and high-starch matrices ensures reliable monitoring for MRL compliance

Future Trends and Potential Applications

Emerging directions include expanding the analyte scope and commodity range, integrating additional isotopic standards, and exploring high-resolution MS for non-target screening. Automation of sample preparation and adopting novel stationary phases or ionization techniques may further improve sensitivity and selectivity. Continued refinement will support multi-residue surveillance programs and regulatory enforcement worldwide.

Conclusion

The validated QuPPe-UPLC-MS/MS method on an ACQUITY UPLC BEH Amide column coupled to a Xevo TQ-S micro demonstrates robust, sensitive, and reproducible analysis of cationic polar pesticides and plant growth regulators. Most compounds meet or exceed EU regulatory requirements, with excellent retention time stability and throughput. Laboratories should perform additional in-house validation to confirm fitness for purpose.

Reference

• European Commission. QuPPe Method V11 (2020).
• European Commission. EU Pesticide Database (2020).
• World Health Organization. International Experts Limit Melamine Levels in Food (2010).
• European Union. SANTE Document No. 12682/2019: Guidance on Analytical Quality Control and Method Validation for Pesticide Residue Analysis (2019).