Determination of Highly Polar Cationic Pesticides and Plant Growth Regulators in Food Using UPLC-MS/MS

Importance of Topic

The determination of highly polar cationic pesticides and plant growth regulators in food commodities is critical for ensuring consumer safety and regulatory compliance. Traditional workflows often struggle with retention and sensitivity for these analytes. The QuPPe (Quick Polar Pesticides) extraction combined with advanced UPLC-MS/MS addresses these challenges by enabling a single, direct analysis of multiple polar compounds across diverse matrices.

Study Objectives and Overview

This application note evaluates the performance of the Waters ACQUITY UPLC I-Class System coupled with the Xevo TQ-S micro mass spectrometer for the simultaneous analysis of ten highly polar cationic pesticides and regulators in apple, cucumber, and wheat flour. Key performance indicators include retention time stability, calibration linearity, method precision, and trueness according to EU SANTE guidelines.

Methodology and Instrumentation

Sample Preparation and Extraction:

• Homogenize 10 g of apple or cucumber (5 g of wheat flour adjusted with 10 mL water).
• Add 10 mL methanol containing 1 % formic acid, vortex, freeze (wheat only), centrifuge, and filter (0.45 µm PVDF).
• Spike filtered extract with analyte mix for calibration and QC.

UPLC-MS/MS Conditions:

• Instrument: ACQUITY UPLC I-Class; Column: BEH Amide 1.7 µm, 2.1 × 100 mm.
• Mobile phases: A: 50 mM ammonium formate (pH 2.9); B: acetonitrile; flow 0.5 mL/min; 10 min gradient.
• MS: Xevo TQ-S micro, ESI+, capillary 0.5 kV, desolvation 600 °C/1000 L/hr, cone gas 150 L/hr.
• MRM transitions optimized for quantifier and qualifier ions per compound.

Main Results and Discussion

Retention and Chromatography:

• All compounds eluted with retention greater than twice the column void volume, exhibiting sharp, symmetric peaks.
• Retention time stability within ±0.1 min across matrices.

Calibration and Linearity:

• Matrix-matched calibration in apple and cucumber from 0.002–0.200 mg/kg; in wheat flour 0.004–0.400 mg/kg (r² > 0.995).
• Back-calculated residuals met SANTE criteria (< 20 %).

Precision and Trueness:

• Fifteen replicate injections at 5 and 20 ng/mL showed accuracy within ±15 % and %RSD < 5 %.
• Ion ratios for qualifier transitions remained within ±30 % of expected values.

Benefits and Practical Applications

The workflow offers a streamlined, single-extraction method capable of detecting multiple polar analytes at low levels with minimal sample handling. High sensitivity and robust performance support routine monitoring of MRL compliance in fruits, vegetables, and cereals without the need for isotopically labeled standards.

Future Trends and Potential Applications

Advances may include integration of high-resolution mass spectrometry for non-target screening, automation of the QuPPe extraction for higher throughput, expansion to more complex food matrices, and incorporation of isotopic standards to further enhance quantitation reliability.

Conclusion

The combination of QuPPe extraction with the ACQUITY UPLC I-Class and Xevo TQ-S micro delivers a robust, sensitive, and reproducible method for the analysis of highly polar cationic pesticides and plant growth regulators in diverse food matrices, fully compliant with EU regulatory guidelines.

Reference

1. European Union Reference Laboratory for Pesticides Single Residue Methods. QuPPe methods (2017).
2. Waters Corporation. A Comprehensive Guide to HILIC (2014).
3. European Commission. EU Pesticide Database (2016).
4. World Health Organization. International Experts Limit Melamine Levels in Food (2010).
5. European Union. SANTE 11813/2017 Guidance Document (2017).