Determination of Pesticide Residues in Drinking Water Using Automated Solid-Phase Extraction and Gas Chromatography with Nitrogen Phosphorus Detection

Significance of the Topic

Organophosphorus pesticides are widely applied in agriculture and can accumulate in water sources, posing acute risks to human and animal health. Sensitive and efficient methods are essential for monitoring these residues in drinking water.

Study Objectives and Overview

This work describes an automated solid phase extraction coupled with gas chromatography using a nitrogen phosphorous detector to quantify eight organophosphorus pesticides in drinking water. The method adapts Chinese standard GB 5750.9-2006 to reduce solvent usage and improve throughput.

Methodology and Experimental Approach

Five hundred milliliter water samples were spiked with mixed standards, methanol, and sodium chloride, then processed on a Dionex AutoTrace 280 SPE system. Elution was performed with ethyl acetate and dichloromethane, and the extracts were concentrated under a gentle nitrogen stream. Final analysis was carried out on a TRACE 1310 GC fitted with a nitrogen phosphorous detector.

Used Instrumentation

• Thermo Scientific Dionex AutoTrace 280 for automated SPE including conditioning, loading, rinsing, and elution.
• Thermo Scientific TRACE 1310 GC with Instant Connect splitless injector and TG-1701 MS capillary column.
• Instant Connect nitrogen phosphorous detector with regulated air, hydrogen, and make-up nitrogen flows.

Main Results and Discussion

• Agela PEP sorbent provided the best retention and elution efficiency when eluted with a 4 mL/4 mL/2 mL mixture of ethyl acetate and dichloromethane.
• Adding 5 g of sodium chloride enhanced salting-out effects, yielding optimal recoveries; reducing nitrogen blow temperature to 30 °C minimized losses of low-boiling analytes.
• Method performance showed linearity from 0.05 to 1 µg/mL (R² > 0.99), detection limits between 0.02 and 0.1 µg/L, recoveries of 83–100 %, and RSDs of 2.4–8.7 %, meeting regulatory requirements.

Benefits and Practical Applications

• The automated SPE–GC workflow lowers solvent consumption and hands-on time, processing six 500 mL samples in under an hour versus five hours manually.
• High selectivity and sensitivity support routine monitoring of organophosphorus pesticide residues in drinking water.
• Modular GC design allows rapid swapping of injector and detector modules for versatile analytical applications.

Future Trends and Possibilities

Integration of online SPE with advanced mass spectrometric detectors can broaden analyte coverage and lower detection limits. Adoption of green solvents, miniaturized extraction devices, and AI-driven data analysis will further enhance environmental monitoring efficiency.

Conclusion

The automated SPE coupled with GC-NPD provides a rapid, sensitive, and reproducible approach for detecting eight organophosphorus pesticides in drinking water, fully complying with Chinese standard GB 5750.9-2006 while reducing solvent use and analysis time.

References

1. Zhou Fang, Sun Cheng, Zhong Ming et al. Solid phase extraction and capillary gas chromatography analysis of residual organophosphorus pesticides in water. Environ. Pollut. Control. 2005, 27(2):151-153.
2. Maciej Tankiewicz, Jolanta Fenik, Marek Biziuk. Determination of organophosphorus and organonitrogen pesticides in water samples. Trends Anal. Chem. 2010, 29(9):1050-1064.
3. Yao Chaoying, Yang Lili, Mu Yingfeng. Determination of demeton in water by gas chromatography. Sichuan Environment. 2007, 26(4):48-50.
4. Chinese Ministry of the Environment. Hygiene Standards for Domestic Drinking Water Method GB5750-2006. Peoples Republic of China.