Analysis of Pesticides Added to Appendix Method 20-2 for the Complementary Items for Water Quality Management in Japan Using a Triple Quadrupole LC/MS/MS

Significance of the Topic

In March 2018, the Japanese Ministry of Health, Labour and Welfare expanded Appendix Method 20-2 for water quality management to include 113 additional pesticides, bringing the total list to 181 compounds. This revision reflects growing regulatory and public health demands for sensitive, comprehensive monitoring of trace pesticides in drinking water.

Study Objectives and Overview

This application note describes the validation of a triple quadrupole LC-MS/MS method (Shimadzu LCMS-8050) for quantifying 99 of the newly added pesticides in tap water, including seven compounds with no prior official methods, several with low target concentrations, and two with more stringent revised limits.

Methodology

Water samples were dechlorinated with sodium ascorbate (or sodium thiosulfate for sensitive analytes), spiked at levels down to one-hundredth of regulatory targets, and analyzed in multiple reaction monitoring (MRM) mode. A metal-free C18 column was employed to minimize adsorption of polar or zwitterionic pesticides. Quantification relied on four-point calibration curves covering concentrations from 0.003 to 100 µg/L, depending on the analyte.

Used Instrumentation

• LC-MS/MS system: Shimadzu LCMS-8050 triple quadrupole with electrospray ionization (ESI) in positive/negative modes
• Column: L-column2 ODS metal-free, 150 × 2.0 mm, 3 µm
• Mobile phases: A = 5 mmol/L ammonium acetate in water; B = 5 mmol/L ammonium acetate in methanol; gradient from 10 % to 100 % B over 46 min
• Flow rate: 0.2 mL/min; column temperature: 40 °C; injection volume: 50 µL
• Interface temperature: 250 °C; DL: 300 °C; block heater: 400 °C; nebulizing gas: 3 L/min; drying gas: 10 L/min; heating gas: 10 L/min

Main Results and Discussion

Spike-and-recovery tests (n = 5) at one-hundredth of target concentrations demonstrated recoveries of 80–113 % and repeatability (RSD) below 18 % for 99 pesticides. Calibration curves exhibited excellent linearity (R2 > 0.997). Newly added pesticides, including propargite, cypermethrin isomers, and methamidophos, were reliably quantified at sub-µg/L levels. Compounds with revised targets (2,4-D, isoxathion) also met stricter criteria, and low-level analytes (e.g., fipronil, cadusafos) achieved limits of quantitation down to 0.003 µg/L.

Benefits and Practical Applications

This validated LC-MS/MS approach enables comprehensive, high-throughput monitoring of a broad pesticide panel in drinking water, supporting regulatory compliance, environmental surveillance, and quality assurance in public and private laboratories.

Future Trends and Opportunities

Further developments may include automation of sample preparation, expansion to emerging contaminants (e.g., metabolites, polar pesticides), and integration with high-resolution MS for non-target screening. Advances in column technology and ionization may enhance sensitivity for challenging analytes.

Conclusion

The Shimadzu LCMS-8050 method meets the stringent requirements of Japan’s Appendix Method 20-2, delivering reliable detection and quantification of 99 additional pesticides at trace levels with high accuracy and precision. This robust workflow ensures effective water quality management and public health protection.

Reference

• Shimadzu Corporation. Application Note LAAN-A-LM-E142, No. C171, June 2018.