Simultaneous Analysis of Pesticides using LC-MS

Significance of the topic

Ensuring safe drinking water requires monitoring a broad spectrum of pesticides. The revised Japanese Water Supply Law sets target values for 101 pesticides in water, and efficient analytical methods are needed to support compliance and public health protection.

Study objectives and overview

This application note presents a simultaneous analysis method for 28 pesticide residues using liquid chromatography–mass spectrometry (LC-MS) in accordance with the Japanese Ministerial Ordinance Additional Method 16. The goal is to quantify each pesticide at 1/100 of its regulatory target concentration in water samples.

Methodology and instrumentation

A highly selective LC-MS approach using selected ion monitoring (SIM) was developed. Key parameters include:

• Column: L-column ODS (150 mm × 2.1 mm I.D.)
• Mobile phase A: 0.1% formic acid in water
• Mobile phase B: Acetonitrile
• Gradient: 0% B (0 min) to 100% B (30–35 min)
• Flow rate: 0.2 mL/min
• Injection volume: 10 µL
• Column temperature: 40 °C
• ESI probe voltages: +4.5 kV (positive), –3.5 kV (negative)
• CDL temperature: 200 °C; nebulizing gas: 1.5 L/min; drying gas: 0.2 MPa

This method detects protonated or deprotonated molecules and, for some analytes, adduct ions. The acetonitrile–formic acid mobile phase was found optimal for ionization and chromatographic separation.

Main results and discussion

SIM chromatograms at 1/100 concentration for all 28 pesticides demonstrated satisfactory signal-to-noise ratios. Both positive and negative ionization modes provided clear, well-resolved peaks. Selectivity was especially high for compounds such as Benomyl, Azoxystrobin, 2,4-D, and Triclopyr. The optimized mobile phase ensured consistent elution and sensitive detection across diverse pesticide chemistries.

Benefits and practical applications

This multi-residue approach streamlines pesticide monitoring workflows, reducing analysis time and solvent consumption. It supports regulatory compliance by achieving required detection limits and provides reliable quantitation for routine water quality testing in environmental and municipal laboratories.

Future trends and potential applications

Advancements may include integration of high-resolution mass spectrometry for even broader compound coverage, automated sample preparation, and on-site portable LC-MS systems. Expanding target lists and coupling with data analytics will enhance environmental monitoring and risk assessment.

Conclusion

The described LC-MS method meets Japanese regulatory requirements for simultaneous quantitation of 28 pesticides in water at stringent detection levels. Its robustness, sensitivity, and selectivity make it a valuable tool for water quality assurance.