Determination of cationic polar pesticides in homogenized fruit and vegetable samples using IC-HRAM MS

Significance of the topic

Polar pesticides are highly polar, ionic, and nonvolatile compounds used as herbicides, desiccants, growth regulators, or fungicides, and their residues in food have become an increasing regulatory and public health concern due to potential toxicity and links to diseases such as Parkinson’s. Ion chromatography combined with high resolution accurate mass spectrometry (IC-HRAM-MS) offers a selective and sensitive solution for multiresidue analysis of cationic pesticides in complex matrices.

Objectives and study overview

This study aims to develop and validate a rapid 10-minute IC-HRAM-MS method for simultaneous determination of six cationic polar pesticides—chlormequat, mepiquat, paraquat, diquat, trimethylsulfonium, and morpholine—in homogenized fruit and vegetable samples, applying full-scan and Parallel Reaction Monitoring (PRM) modes on a Thermo Scientific Q Exactive Orbitrap mass spectrometer.

Methodology and instrumentation

Sample Preparation
Add 10 mL water to 10 g homogenate, shake, extract with 30 mL cold methanol, centrifuge, filter through 0.2 µm, and dilute 10-fold.

Instrumentation

• Dionex Integrion HPIC system with RFIC eluent generation, CR-CTC trap, and CERS-500e suppressor
• IonPac CG17 guard (2×50 mm) and CS17 separation column (2×250 mm)
• Suppressed conductivity and HRAM-MS detection with Q Exactive Focus Orbitrap and HESI II source
• Auxiliary pumps for suppressor regenerant and acetonitrile makeup
• Software: Foundation 3.0, Xcalibur, TraceFinder, with virtual channels and conductivity triggers for method robustness

Key results and discussion

• A 2–60 mM methanesulfonic acid gradient (10 min, 0.4 mL/min, 40 °C) achieved baseline separation of four analytes; diquat and paraquat coeluted but were resolved by high-resolution PRM
• Limits of detection ranged from 0.1 to 1.1 µg/L with linear dynamic range (0.2–20 µg/L, r² > 0.98)
• Mass accuracy was within ±1.1 ppm, fulfilling SANTE guidelines (<5 ppm)
• Recoveries of spiked samples were 80–120% for green bean, pear, and apple matrices; lower recoveries (70–78%) were observed in squash

Benefits and practical applications

• Rapid multiresidue screening suitable for routine quality control and regulatory compliance
• Reduced analysis time and simplified sample preparation compared to conventional LC-MS methods
• High selectivity for ionic pesticides and minimal matrix interferences
• Real-time consumable tracking and automated suppressor protection enhance method robustness

Future trends and potential applications

• Extension to additional ionic contaminants and pesticide metabolites across diverse food and environmental matrices
• Coupling with advanced orbitrap platforms for ultra-low level quantitation
• High-throughput and automated workflows for large-scale monitoring programs
• Integration of IC-HRAM-MS with data analytics and digital libraries for trend analysis and risk assessment

Conclusion

This study demonstrates a 10-minute IC-HRAM-MS workflow for six cationic polar pesticides in fruits and vegetables, delivering excellent mass accuracy, sensitivity, and robust recoveries across multiple matrices. The method’s speed, selectivity, and automated system controls support its adoption for routine pesticide residue analysis under strict regulatory demands.

References

1. European Union Reference Laboratory for Fruits and Vegetables (EURL-FV) J. AOAC Int. 2018 101(2) 352–359
2. Thermo Scientific Application Note AN-661 Fast analysis of polar pesticides in foods by suppressed IC-MS
3. Thermo Scientific Application Note AN-666 Analysis of polar pesticides in water at low ng/L by IC-MS/MS
4. Madden JE et al. EPRW 2018 presentation on cationic pesticide determination by IC-MS/MS
5. SANTE/11813/2017 EU guidelines for mass accuracy and method validation