Extract Nonvolatile Pesticides from Drinking Water, Using a Graphitized Carbon Adsorbent

Significance of Topic

Monitoring nonvolatile pesticides such as carbamates and thioureas in drinking water is critical for environmental safety and public health. Efficient extraction and concentration methods are needed to achieve reliable quantification, reduce solvent use, and enable high sample throughput.

Objectives and Overview of the Study

This study evaluates a solid phase extraction (SPE) protocol using a graphitized carbon adsorbent (Supelclean ENVI-Carb) to recover 14 nonvolatile pesticides from drinking water. Comparative performance against C8/C18 silica-based SPE and traditional liquid–liquid extraction was assessed in terms of recovery, reproducibility, and processing speed.

Methodology

The extraction workflow comprises:

• Tube conditioning with methylene chloride/methanol and dilute acetic acid in water
• Loading 100 mL to 1 L water samples (10–50 µg/L pesticide spike) at ~5 mL/min
• Vacuum drying for 1 minute
• Elution of analytes with methanol and methylene chloride/methanol
• Concentration under nitrogen to ~400–500 µL and reconstitution to 1 mL
• Injection of 20 µL into HPLC-UV

Used Instrumentation

The analysis employed HPLC-UV with a SUPELCOSIL LC-18-DB column (25 cm × 4.6 mm, 5 µm) and a water–acetonitrile gradient (initial 90:10 to 30 % B over 30 minutes) at 1.5 mL/min. Detection was at 220 nm; no derivatization was required, facilitating automation.

Main Results and Discussion

ENVI-Carb SPE delivered consistently high recoveries (95–98 % ±3–6 %) for carbamate and thiourea pesticides, outperforming C8/C18 silica (recoveries often <75 % for polar analytes) and liquid–liquid extraction. Variability was lower (±3–6 %) compared to silica-based methods (±8–16 %). The nonporous carbon phase allowed rapid processing without loss of capacity, despite a lower surface area.

Benefits and Practical Applications

• Superior recovery and reproducibility for polar and nonpolar pesticides
• Reduced processing time due to nonporous adsorbent
• Lower solvent consumption and elimination of glassware-intensive liquid–liquid steps
• Compatibility with automation for high-throughput environmental monitoring and QA/QC workflows

Future Trends and Potential Uses

Advancements may include coupling ENVI-Carb SPE with mass spectrometry for enhanced sensitivity and specificity, miniaturized high-throughput formats, exploration of novel carbon-based materials to extend analyte scope, and integration into green analytical protocols using alternative solvents.

Conclusion

The Supelclean ENVI-Carb SPE method offers an effective, robust approach for extracting nonvolatile pesticides from drinking water, achieving high recoveries, low variability, and rapid processing. It represents a valuable tool for environmental testing laboratories seeking reliable, automated workflows.

References

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