Identification and Quantitation of Herbicides and Pesticides in Water by LC and Diode Array Detector

Significance of the Topic

Mass monitoring of herbicides and pesticides in water is critical for environmental safety and regulatory compliance. The cited regulation in France and other European countries highlights the need for robust analytical methods able to detect a broad range of contaminants at trace levels. This methodology addresses these practical demands by combining sensitive extraction and detection techniques.

Aims and Overview of the Study

The study aimed to develop a comprehensive HPLC-DAD method to identify and quantify 36 commonly used herbicides and pesticides, including the 17 compounds specified by DIN 38-407, Part 12. The approach extends beyond regulatory requirements to include additional agriculturally relevant analytes, offering broad applicability in environmental monitoring.

Applied Methodology

• Sample Preparation: Solid Phase Extraction using Empore C18 disks; conditioning with dichloromethane/ethyl acetate (1:1), methanol and water; 1 L of water sample loaded; elution with ethyl acetate and dichloromethane mixtures; evaporation and reconstitution in methanol.
• Chromatographic Separation: HPLC on a TSK ODS 80 column (5 µm, 25 cm × 4.6 mm) at 40 °C; gradient from 100% aqueous phase (ammonium acetate with 2% acetonitrile and methanol) to 80% organic phase (acetonitrile with additives) over 105 minutes.

Instrumental Setup

• Detector: Polychrom® 9065 Diode Array Detector set at 239 nm; additional data acquired at 220 nm, 230 nm and 244 nm for enhanced sensitivity of specific compounds.
• Data Processing: PolyView™ automated spectral library search using retention time windows and purity parameters to confirm peak identity based on similarity/dissimilarity metrics.

Main Results and Discussion

The method effectively separated all 36 target compounds in a single run, with clear chromatographic resolution as illustrated in the standard mix and environmental water samples. Library search confirmed identities with high purity parameters (PuP) and similarity scores (>0.999). Recoveries for the 17 DIN-specified herbicides ranged from 67 % to 93 %, demonstrating reliable extraction and quantitation performance at 0.5 µg/L levels.

Benefits and Practical Application of the Method

• Wide analyte scope covering regulatory and additional agrochemicals in one assay.
• High confidence in compound identification through diode array spectral matching.
• Sufficient sensitivity and reproducibility for trace-level quantitation in environmental water.
• Adaptable run time for focused monitoring of specific compound subsets.

Future Trends and Potential Applications

• Integration with mass spectrometry for enhanced selectivity and lower detection limits.
• Automation of SPE and data evaluation for high-throughput analysis.
• Development of rapid screening protocols using shorter gradients and advanced column chemistries.
• On-site and real-time monitoring tools leveraging portable HPLC-DAD platforms.

Conclusion

This HPLC-DAD method provides a robust, reliable workflow for simultaneous analysis of a broad spectrum of herbicides and pesticides in water. It fulfills regulatory demands and offers flexibility for comprehensive environmental surveillance, paving the way for further technological enhancements and operational efficiencies.