Determination of Pesticides in Drinking Water with SPDE-GC/MS

Importance of the Topic

Intensive use of pesticides in agriculture poses a significant risk to groundwater and drinking water due to high persistence and water solubility of many compounds. Chronic exposure at trace levels, including those suspected of endocrine disruption, requires continuous monitoring to ensure compliance with stringent regulations and protect public health.

Objectives and Overview

This study evaluates a fully automated solid-phase dynamic extraction (SPDE) coupled with gas chromatography/mass spectrometry (GC/MS) for quantifying a range of legacy and current-use pesticides in drinking water at ultra-trace levels. The approach aims to demonstrate sensitivity down to the low parts-per-trillion range, minimal solvent consumption and suitability for routine analysis.

Methodology and Instrumentation

The workflow integrates SPDE sample preparation on a CTC CombiPAL autosampler with subsequent GC/MS analysis. Key parameters are:

• SPDE conditions: CHROMTECH SMM coating on syringe needle; 20 mL vials; 50 °C; 90 extraction strokes at 1 mL each; 500 rpm agitation; 1 mL desorption gas at 50 µL/s; 60 s pre-desorption.
• GC conditions: Agilent 6890N with Varian VF-5 MS column (30 m × 0.25 mm × 0.25 µm); oven ramp from 70 °C (1 min) at 15 °C/min to 320 °C (10 min); splitless injection (250 °C), purge 30 mL/min; helium carrier at 1.2 mL/min.
• MS conditions: KODIAK 1500 with EI source at 70 eV, 230 °C; GC interface at 280 °C; SIM mode (0.7 u, 300 ms dwell) targeting characteristic ions for 16 analytes.

Main Results and Discussion

Analysis of a pesticide standard mixture (2.5 ppm) confirmed retention times and SIM transitions for key analytes (lindane isomers, heptachlor, aldrin, DDT series, endosulfan, dieldrin, endrin, methoxychlor). Progressive dilutions down to 2.5 ppt yielded clear SIM signals in total ion current traces, demonstrating reliable identification and quantitation at ultra-trace levels. Automation provided high reproducibility and minimal sample handling.

Benefits and Practical Applications

The SPDE-GC/MS method offers:

• High sensitivity enabling detection in the low ppt range.
• Fully automated sample enrichment without toxic solvents.
• Low sample volume requirements (10–20 mL).
• Compact footprint using existing autosampler infrastructure.
• Reduced matrix interferences and robust quantitation for routine monitoring.

Future Trends and Applications

Advances may include novel sorptive coatings for broader analyte coverage, faster extraction cycles for higher throughput and integration with high-resolution MS for enhanced selectivity. Coupling SPDE with ambient ionization could expand applications to untreated environmental samples and real-time screening.

Conclusion

SPDE-GC/MS represents a powerful, eco-friendly solution for routine monitoring of pesticide residues in drinking water. The method delivers automated, solvent-free extraction with ppt-level sensitivity, meeting regulatory demands and safeguarding water quality.

References

• RIVM National Institute of Public Health and Environmental Protection, Pesticide Leaching Assessment, 1992.
• Chromtech GmbH, Application Note SP303e: Determination of Pesticides in Drinking Water with SPDE-GC/MS, 05/2003.