The Multi-Residue Analysis of Polar Anionic Pesticides using IC-MS/MS

Importance of the Topic

Polar anionic pesticides such as glyphosate, glufosinate and fosetyl are widely used worldwide and can remain as residues in food commodities

Their high polarity and ionic character complicate extraction and analysis compared to more hydrophobic pesticides

Sensitive and robust multi-residue methods are essential to support regulatory monitoring and ensure food safety

Study Objectives and Overview

The study aimed to develop and validate an integrated sample-to-result workflow for quantifying polar anionic pesticides in wheat flour using ion chromatography tandem mass spectrometry (IC-MS/MS)

It adapted the QuPPe extraction procedure to streamline sample preparation and combined it with high performance ion chromatography and triple quadrupole mass spectrometry for simultaneous analysis of multiple targets

Methodology and Instrumentation

Sample preparation involved water and methanol extraction, freezing at –20°C, centrifugation, tenfold dilution, solid phase clean-up on reverse phase cartridges and final filtration

Analysis was performed on a Thermo Scientific Dionex Integrion HPIC system with Reagent-Free IC, an AS19 anion exchange column at 40°C, a Dionex ADRS 600 suppressor, and a TSQ Altis triple quadrupole mass spectrometer

Key parameters included a 21 minute gradient elution with KOH eluent suppressed to water, 0.35 mL/min flow rate with acetonitrile makeup, 25 µL injection volume and SRM transitions for quantifier and qualifier ions

Isotopically labeled internal standards were employed to correct matrix effects and improve accuracy, while a divert valve minimized matrix load to the detector and MS source

Main Results and Discussion

Chromatographic separation of 15 target analytes was achieved in a 21 minute runtime with baseline resolution

Recoveries ranged from 70 to 120 percent at two spiking levels in wheat flour with repeatability RSDs below 20 percent and linearity coefficients above 0.995

Sensitivity met maximum residue limits set by regulatory bodies in the EU, US, Japan and China

Clean-up steps and internal standards effectively reduced matrix interferences and improved quantitative accuracy

System robustness was demonstrated over more than 80 wheat flour injections with stable retention times (variation ±0.09 min) and consistent peak shapes

Benefits and Practical Applications

This workflow allows simultaneous quantification of multiple polar anionic residues without derivatization or ion pairing agents

High capacity ion exchange columns tolerate larger sample loads for trace analysis in complex matrices such as cereals

The method can be implemented for routine quality control in the food industry and regulatory monitoring programs

Future Trends and Possibilities

Extension to additional food matrices including fruits, vegetables and processed products

Development of new isotopically labeled standards for compounds not currently covered

Integration with high resolution mass spectrometry for broader screening of anionic contaminants

Automation of sample clean-up and data analysis to increase throughput and reduce labor

Conclusion

The presented IC-MS/MS workflow offers a sensitive, accurate and reliable solution for multi-residue analysis of polar anionic pesticides in wheat flour

Its validated performance meets international regulatory requirements and provides a foundation for expanded food safety testing

References

• Anastassiades M et al Quick method for the analysis of highly polar pesticides in plant origin via LC-MS/MS involving methanol extraction (QuPPe) version 10.1 2019
• SANTE/11813/2017 Guidance on analytical quality control and method validation procedures for pesticide residues analysis in food and feed 2017