Determination of four polar pesticides in drinking water by IC-MS

Importance of the Topic

Pesticides such as glyphosate, glufosinate, endothall and AMPA pose analytical challenges due to their high polarity and lack of chromophores. Routine monitoring in drinking water is crucial for regulatory compliance and public health. Coupling ion chromatography with mass spectrometry enables direct, sensitive detection of ionic pesticides without elaborate derivatization.

Goals and Study Overview

This work aimed to develop and validate a single-method IC-MS procedure capable of simultaneously quantifying four polar pesticides in potable water. The study focused on method sensitivity, selectivity, reproducibility and applicability to real-world samples using a single quadrupole MS detector.

Methodology and Instrumentation

The approach uses a Thermo Scientific Dionex Integrion HPIC system with Reagent-Free™ eluent generation and a 2×250 mm IonPac AS19-4µm anion-exchange column. A dynamic suppressor (Dionex ADRS 600) operates in external water mode via an auxiliary Dionex AXP-MS pump. The eluate is directed through a conductivity detector then diverted to an ISQ EC single quadrupole mass spectrometer with a HESI-II probe under negative electrospray ionization. Selected ion monitoring tracks target masses for glufosinate, AMPA, endothall, glyphosate and their isotopically labelled internal standards. Sample injection volume is 10 µL with a 25 min gradient (14–80 mM KOH).

Main Results and Discussion

Chromatographic separation of the four analytes and common anions was achieved within 25 min with baseline resolution. Method detection limits ranged from 0.10 to 0.33 µg/L and LODs from 0.08 to 0.33 µg/L. LCMRL values were established between 0.31 and 0.75 µg/L. Calibration was linear (r²>0.999) over 0.5–100 µg/L. Recoveries in spiked drinking water (1–10 µg/L) ranged from 94% to 105%. Repeatability showed retention time RSD <0.24% and peak area RSD <2.43%. Studies in a high-anion synthetic matrix highlighted the need for isotopic internal standards to offset ion suppression.

Benefits and Practical Applications

• Eliminates derivatization, reducing sample preparation time and potential errors.
• Simultaneous determination of four regulated pesticides and metabolites.
• Enhanced sensitivity and selectivity with minimal matrix interferences.
• Cost-effective integration of single quadrupole MS simplifies routine monitoring workflows.

Future Trends and Possibilities

Advances may include high-resolution MS for expanded multi-residue workflows, micro- or nano-scale IC to reduce solvent use, automated sample preparation, and real-time monitoring devices. Data analytics and machine learning could further enhance detection and quantification of emerging polar contaminants.

Conclusion

The developed IC-MS method offers a robust, sensitive and streamlined approach for monitoring four key polar pesticides in drinking water. Its direct injection workflow, strong reproducibility and compliance with regulatory detection limits position it as a valuable tool for environmental and water-quality laboratories.

References

1. IARC Monograph on Glyphosate and Related Compounds.
2. USGS Reports on Glyphosate Occurrence in Wastewater.
3. EPA Method 547 and 548 for Glyphosate and Endothall in Drinking Water.
4. ICH Guideline Q2B on Analytical Method Validation.
5. Thermo Fisher Scientific Technical Notes and Instrument Manuals.