Analysis of Organophosphorus Pesticides in Drinking Water using SPME-GCMS

Significance of the Topic

Organophosphorus pesticides are widely used insecticides that pose serious health risks through water contamination. Monitoring their residues in drinking water is critical to protect public health and comply with regulatory standards.

Objectives and Study Overview

This study evaluates an automated solid phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS) method for the simultaneous analysis of five organophosphorus pesticides (Diazinon, Parathion, Phenitrothion, Phenthoate and EPN) in drinking water using Shimadzu instrumentation.

Instrumentation

• Autosampler: Shimadzu AOC-6000 Plus for fiber conditioning, sample incubation and injection automation
• Analyzer: Shimadzu GCMS-QP2020 NX in selected ion monitoring (SIM) mode
• SPME fiber: 100 µm polydimethylsiloxane (PDMS)
• GC column: SH-5, 30 m × 0.25 mm I.D., 0.25 µm film thickness
• Gas flow: 1.5 mL/min; injection split ratio 5:1; injector 250 °C; interface 250 °C; ion source 230 °C

Methodology

Sample incubation was conducted at 70 °C for 5 min followed by 15 min extraction and 5 min desorption. The GC temperature program ramped from 70 °C to 350 °C under SIM targeting characteristic m/z ions for each pesticide. Calibration standards ranged from 0.1 to 10 µg/mL with 1 µg/mL triphenyl phosphate as internal standard. Method detection limits (MDL) and limits of quantitation (LOQ) were determined from seven replicates at 0.5 ng/mL.

Key Results and Discussion

• Linearity: R² ≥ 0.998 for all analytes over 0.1–10 µg/mL.
• MDL: 0.03–0.06 ng/mL; LOQ: 0.10–0.20 ng/mL.
• Accuracy: 87.6%–108.2%; Precision: 2.2%–4.9% at 5 ng/mL.
• Automated SPME reduced solvent use and manual handling while maintaining robust analytical performance.

Practical Applications and Benefits

The validated method meets drinking water quality criteria for organophosphorus pesticides, offering high sensitivity, reproducibility and throughput. Automation minimizes operator error and accelerates routine analysis in environmental monitoring and quality control laboratories.

Future Trends and Potential Applications

• Coupling with high-resolution MS to expand analyte scope.
• Development of portable SPME-GC systems for on-site water testing.
• Integration of multi-residue protocols including broader pesticide classes.
• Advanced automation for higher sample throughput and streamlined data analysis.

Conclusion

The SPME-GC-MS method using Shimadzu AOC-6000 Plus and GCMS-QP2020 NX provides a reliable, sensitive, and fully automated approach for the determination of organophosphorus pesticides in drinking water, fulfilling regulatory requirements with exemplary analytical performance.

Reference

[1] National Institute of Environmental Research. Environmental Standards for Drinking Water Pollution, Organophosphorus Pesticides–Solid Phase Microextraction (SPME)-Gas Chromatography-Mass Spectrometry (ES 05501.5), 2022-36.