Analytical Data for Agricultural Chemicals as Water Quality Control Target Setting Items

Significance of the topic

The continual introduction and use of agricultural chemicals pose significant risks to drinking water quality. National regulatory bodies in Japan regularly update water quality control target values for pesticides to protect public health. Comprehensive analytical methods are required to detect and quantify dozens of compounds at trace levels (sub–μg/L to mg/L), ensuring that treated water meets established standards.

Objectives and Overview

This application note compiles validated analytical data for 15 water quality control target pesticides (totaling 102 components), illustrating sample preparation protocols, instrumental settings, and performance metrics. The goal is to provide water suppliers and environmental laboratories with reliable, reproducible methods for routine monitoring.

Methodology and Instrumentation

• Sample Pretreatment: Solid-phase extraction (SPE) on styrene-divinylbenzene-C18 or divinylbenzene-methacrylate cartridges; solvent extraction of polar herbicides; derivatization strategies (methyl esterification, FMOC tagging, OPA post-column) to enhance volatility or fluorescence.
• Gas Chromatograph–Mass Spectrometry (GC-MS): Rtx-5MS columns, splitless injection, programmed temperature ramps, selective ion monitoring (SIM) for up to 83 pesticides (Method 5) and additional methylated acids (Method 6).
• High-Performance Liquid Chromatography (HPLC): UV detection at dual wavelengths (230/270 nm) for iprodione, asulam, thiophanate-methyl, siduron (Method 9); post-column o-phthalaldehyde fluorescence for carbofuran, carbaryl, methomyl (Method 14); ninhydrin derivatization for iminoctadine acetate with fluorescence detection (Method 17).
• Liquid Chromatograph–Mass Spectrometry (LC-MS): ESI-positive and –negative modes to simultaneously quantify 30 pesticides (Method 18), using a formic acid water/acetonitrile gradient, multiple reaction monitoring with limits of detection in the 0.005–0.3 mg/L range.

Main Results and Discussion

• GC-MS Methods achieved limits of quantitation down to 0.0001–0.0005 mg/L with repeatability (CV) generally below 5 % for over 80 compounds.
• Derivatization strategies improved detection of polar pesticides, yielding stable methyl-ester signals with CVs under 4 %.
• HPLC-UV and post-column fluorescence approaches separated key herbicides and insecticides at concentrations equivalent to 1–5 % of target values, enabling clear baseline resolution.
• LC-MS demonstrated simultaneous analysis of 21 positive-mode and 9 negative-mode pesticides, offering robust SPE cleanup and precise quantitation at regulatory limits.

Practical Benefits and Applications

• Standardized protocols enable routine laboratory implementation for water quality control, ensuring compliance with Japanese Water Supply Act requirements.
• SPE and derivatization workflows can be tailored to emerging pesticides and matrix variations, improving adaptability for different water sources.
• Validated instrumental conditions support high throughput and inter-laboratory reproducibility.

Future Trends and Applications

• Adoption of high-resolution mass spectrometry (HRMS) for broader screening of new pesticide classes and metabolites.
• Automation of sample preparation (online SPE, robotic liquid handling) to increase throughput and reduce human error.
• Development of miniaturized and field-deployable sensors for real-time water monitoring.
• Integration of data-driven approaches and spectral libraries to accelerate method development and compound identification.

Conclusion

Through rigorous validation of SPE, derivatization, and chromatographic-mass spectrometric methods, this work provides a comprehensive toolkit for monitoring a wide array of agricultural chemicals at trace levels in drinking water. The approaches satisfy current regulatory standards and establish a foundation for future method enhancements.

References

• Ministry of Health, Labour and Welfare (Japan). Health Service Bureau, Water Supply Div. Ordinance No. 1010001, October 10, 2003.