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

Significance of the Topic

Glyphosate, endothall, AMPA, and glufosinate are widely used polar pesticides that pose challenges for drinking water analysis due to their ionic nature and lack of chromophores. Sensitive, direct detection methods are essential to meet regulatory limits and ensure public health.

Objectives and Study Overview

The objective was to develop a derivatization-free IC-MS method to simultaneously quantify four polar pesticides and their primary metabolite in drinking water, validating performance metrics such as sensitivity, accuracy, precision, and matrix compatibility.

Methodology and Instrumentation

• Instrumentation:
  • Thermo Scientific Dionex Integrion HPIC system with RFIC™ eluent generation
  • Dionex IonPac AG19-4μm guard and AS19-4μm analytical columns
  • Thermo Scientific Dionex ADRS 600 externally regenerated suppressor
  • ISQ™ EC single quadrupole MS with HESI-II probe
  • Dionex AXP-MS auxiliary pump for suppressor regeneration
  • Chromeleon™ CDS software v7.2.9
• Elution: KOH gradient (14–80 mM) at 0.4 mL/min, 25 min run
• Detection:
  • Suppressed conductivity for chromatographic profiling
  • Negative-mode ESI-SIM (m/z 168–185) for analyte confirmation
• Calibration: Internal standard calibration using isotopically labeled analogues (10 µg/L), 0.5–100 µg/L range, r² > 0.999
• Sample Preparation: Direct injection (10 µL) of ethylenediamine-preserved water samples

Main Results and Discussion

• Baseline separation of target analytes and common anions achieved within 25 min.
• LODs: 0.08–0.33 µg/L; MDLs matched LODs; LCMRLs: 0.31–0.75 µg/L.
• Calibration linearity with r² > 0.999 across the working range.
• Recovery in drinking water and synthetic matrix: 91–105% for all pesticides.
• Precision: Retention time RSD < 0.24%; peak area RSD < 2.5% over three days.
• Matrix effects: up to a 45% ion suppression observed for endothall and glyphosate in high-ionic matrices, effectively corrected by internal standards.

Benefits and Practical Applications of the Method

• Single method quantifies four regulated ionic pesticides without derivatization.
• Direct injection minimizes sample preparation, reducing analysis time and potential errors.
• Cost-effective use of a compact single quadrupole MS system.
• Suitable for routine monitoring in drinking water and environmental matrices.

Future Trends and Potential Applications

• Coupling with tandem or high-resolution MS for enhanced selectivity and lower detection limits.
• Development of portable IC-MS platforms for in-field water quality monitoring.
• Extension to other ionic pollutants, including emerging herbicides and metabolites.
• Integration with advanced data analytics for real-time compliance tracking.

Conclusion

A robust IC-MS approach was established for direct analysis of glyphosate, AMPA, glufosinate, and endothall in drinking water, delivering high sensitivity, precision, and accuracy without the need for derivatization, streamlining workflows and meeting regulatory requirements.

References

1. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 112, 2015.
2. US Geological Survey. Glyphosate Found in Wastewater Discharge to Stream, 2020.
3. US EPA Method 547: Direct-Aqueous-Injection HPLC for Glyphosate in Drinking Water, 2008.
4. US EPA Method 548.1: Endothall by GC-MS with Derivatization, 1990.
5. US EPA Method 300.1: Inorganic Anions by Ion Chromatography, 1997.
6. Thermo Fisher Scientific. Dionex Integrion HPIC System Operator’s Manual, P/N 22153-97003.
7. Thermo Fisher Scientific. ISQ EC Mass Spectrometer Operating Manual, P/N 1R120591-0002.
8. Thermo Fisher Scientific. Technical Note TN-72611: IC-MS System Configuration and Optimization.