Analysis of Regulated Pesticides in Drinking Water Using Accela and EQuan

Significance of the Topic

The control and monitoring of pesticide residues in drinking water are essential to protect human health and comply with stringent regulatory standards. Many pesticides require detection limits at parts-per-trillion levels, a challenge for conventional analytical workflows. The development of rapid, sensitive and automated methods that eliminate lengthy offline sample preparation is critical for high-throughput water quality testing.

Objectives and Overview

This study demonstrates an integrated approach combining Fast-HPLC, an online sample enrichment system (EQuan), and tandem mass spectrometry for the quantification of eleven regulated pesticides in drinking water at sub-ppb concentrations. The method aims to achieve full chromatographic separation and quantification within a six-minute run, including direct injection of large sample volumes.

Methodology and Instrumentation

• Sample Preparation: Bottled water samples were spiked with eleven pesticides (e.g., carbofuran, azoxystrobin, tricyclazole) over a concentration range of 0.5–1000 pg/mL without offline cleanup.
• Online Enrichment and Chromatography: A 1 mL injection onto a Hypersil GOLD 20×2.1 mm (12 µm) loading column in high-aqueous mobile phase at 1 mL/min. After one-minute loading, a six-port valve switched flow to back-flush analytes onto a Hypersil GOLD 50×2.1 mm (1.9 µm) analytical column, using a water/acetonitrile gradient with 0.1% formic acid.
• Mass Spectrometry: A TSQ Quantum Access triple quadrupole with heated electrospray ionization in positive mode (spray voltage 4000 V, vaporizer at 450 °C, nitrogen sheath/auxiliary gas at 50 units). Selected reaction monitoring transitions and collision energies were optimized for each compound.

Key Results and Discussion

• Chromatographic Performance: All eleven pesticides eluted within three minutes under Fast-HPLC conditions, compared to nearly eight minutes in a standard HPLC run.
• Analytical Sensitivity: Limits of detection ranged from 0.5 to 100 ppt, with calibration linearity (R² > 0.99 for most analytes) over three orders of magnitude.
• Regulatory Compliance: Quantification was achieved well below Japanese Ministry of Health, Labour and Welfare Minimum Performance Reporting Limits (MPRLs).

Benefits and Practical Applications

The integrated Fast-HPLC and EQuan approach eliminates offline concentration steps, reducing total analysis time by more than two-thirds and enhancing laboratory throughput. The method delivers reliable sub-ppb detection for routine drinking water monitoring, quality assurance, and regulatory reporting.

Future Trends and Applications

• Further miniaturization and microfluidic LC systems for even faster separations.
• Expanded pesticide panels and multiclass contaminant screening in environmental matrices.
• Automation and integration with laboratory information management systems for continuous monitoring.
• Advances in high-resolution mass spectrometry for improved specificity and quantitation.

Conclusion

The combination of Fast-HPLC, online pre-concentration using EQuan, and triple quadrupole LC-MS/MS provides a rapid and sensitive platform for detecting low-level pesticide residues in drinking water. This streamlined workflow meets regulatory requirements while significantly improving sample throughput and operational efficiency.

Reference

1. Japanese Ministry of Health, Labour and Welfare. Minimum Performance Reporting Limits for Pesticides.