High Speed Analysis of Pesticides Listed in 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

The monitoring of trace pesticide residues in drinking water is essential for ensuring public health and regulatory compliance. Recent updates to Japan’s water quality standards expanded the list of target compounds from 68 to 181, requiring faster and more reliable analytical methods.

Objectives and Study Overview

This study presents a high‐speed simultaneous analysis of 181 pesticides listed in Appendix Method 20‐2 using a triple quadrupole LC/MS/MS system. It also evaluates the performance of the LCMS‐8050 for 152 of these compounds under drinking water inspection guidelines.

Methodology and Instrumentation

Sample Preparation:

• Tap water was dechlorinated with sodium ascorbate or sodium thiosulfate.
• Samples were spiked at 1/100 of regulatory target values, without solid‐phase extraction.

Chromatography and Mass Spectrometry:

• Column: InertSustain AQ‐C18 PEEK (50×2.1 mm, 1.9 µm).
• Mobile phase A: 5 mmol/L ammonium acetate in water; B: 5 mmol/L ammonium acetate in methanol.
• Gradient: 10→45→80→100→10 % B over 25 min at 0.25 mL/min, 40 °C.
• Injection: 50 µL, ESI in positive/negative modes.
• MS parameters: DL 200 °C, interface 200 °C, block heater 400 °C, nebulizing gas 3 L/min, drying gas 10 L/min, heating gas 10 L/min.

Main Results and Discussion

TIC chromatograms demonstrated complete separation of all 181 pesticides within 25 minutes. Seven newly added pesticides (propargite, cypermethrin isomers, ethiprole, fenoxanil, methamidophos, tolfenpyrad) exhibited linear calibration (R2 > 0.998) and clear MRM peaks at 1/100 target concentrations. In spike‐and‐recovery tests for 152 compounds:

• Recovery rates ranged from 80 % to 113 %.
• Repeatability (%RSD) was below 15 % for nearly all analytes.

These results meet or exceed regulatory requirements, indicating robust method performance across diverse pesticide chemistries.

Practical Benefits and Applications

The method offers high throughput, reduced solvent use, and broad applicability for routine QA/QC and regulatory laboratories. It enables simultaneous screening of a large number of pesticides in a single run, facilitating rapid decision‐making in water quality management.

Future Trends and Possibilities

Further improvement may include:

• Integration with automated sample pretreatment systems.
• Expansion to emerging contaminants beyond the current pesticide list.
• Coupling with high‐resolution mass spectrometry for non‐target screening.
• Application of advanced data‐processing algorithms and AI‐driven workflows for real‐time monitoring.

Conclusion

This study demonstrates that a triple quadrupole LC/MS/MS system equipped with a metal‐free ODS column can rapidly and accurately analyze 181 regulated pesticides in drinking water. The validated method fulfills strict recovery and repeatability criteria, supporting comprehensive and efficient water quality monitoring.

Used Instrumentation

• Shimadzu LCMS‐8050 triple quadrupole LC/MS/MS
• InertSustain AQ‐C18 PEEK column (50 mm × 2.1 mm I.D., 1.9 µm)