Analysis of Iminoctadine, Diquat and Paraquat

Importance of the Topic

Environmental monitoring of herbicides such as iminoctadine, diquat and paraquat is critical for ensuring safe drinking water and compliance with regulatory standards. The polar nature of these quaternary ammonium compounds poses analytical challenges for reverse-phase chromatography, while sensitive detection at trace levels demands robust mass spectrometric techniques.

Objectives and Study Overview

This application study describes the development of a rapid, sensitive and reliable LC–MS/MS method using hydrophilic interaction liquid chromatography (HILIC) for the simultaneous analysis of iminoctadine, diquat and paraquat in tap water at sub-ppb concentrations. The goal was to achieve low limits of detection, high throughput and straightforward sample handling suitable for routine water quality management.

Methodology and Instrumentation

A Shim-pack Velox HILIC column (100 mm × 2.1 mm I.D., 2.7 µm) was employed under isocratic conditions with 50 % acetonitrile and 150 mmol/L ammonium formate buffer. The flow rate was set at 0.40 mL/min, column temperature at 30 °C, and injection volume at 5 µL. Mass spectrometric detection was performed on an LCMS-8060 system with electrospray ionization in positive mode, using multiple reaction monitoring (MRM) transitions:

• Iminoctadine: m/z 178.90 → 69.10
• Diquat: m/z 183.10 → 157.10
• Paraquat: m/z 186.10 → 171.10

Main Results and Discussion

The method achieved clear separation and symmetrical peak shapes for all three analytes within a short run time. Calibration curves were linear across the tested range, with a limit of detection of 0.02 µg/L for each compound. The use of HILIC allowed efficient retention of these polar herbicides without extensive sample preparation or ion-pair reagents. Reproducibility tests demonstrated consistent retention times and signal intensities, indicating suitability for routine monitoring.

Benefits and Practical Applications

– High sensitivity and selectivity for quaternary ammonium herbicides at trace levels
– Simplified isocratic HILIC separation reduces mobile-phase complexity and equilibration time
– Minimal sample pretreatment accelerates workflow for water quality laboratories
– Compatibility with high-throughput screening in environmental monitoring and regulatory compliance

Future Trends and Potential Applications

Advances in stationary phases and faster mass analyzers will further enhance throughput and sensitivity. The method can be expanded to a broader panel of polar pesticides and transformation products. Integration with automated sample preparation systems and online solid-phase extraction may deliver fully automated workflows for large-scale water quality surveillance.

Conclusion

A HILIC-MS/MS approach using the Shim-pack Velox column and Shimadzu Nexera X2/LCMS-8060 instrumentation provides a powerful solution for trace-level determination of iminoctadine, diquat and paraquat in tap water. The method combines fast analysis, low detection limits and operational simplicity, meeting the demands of modern environmental testing.

Reference

• Application News an_01-00254 (JP, ENG), Shimadzu Corporation, First Edition: Aug. 2023, ERAS-1000-0453