Improving Sample Preparation and Analysis for Organochlorine Pesticides Using an Optimized Extraction and Analytical Technique

Significance of the Topic

Organochlorine pesticides, despite being banned for decades, persist in water and soil, posing ongoing risks to ecosystems and human health. Environmental laboratories face high sample volumes and tight deadlines, driving the need for faster, cost-effective preparation and analysis methods.

Objectives and Study Overview

This study aimed to:

• Evaluate Resprep® CarboPrep Plus SPE cartridges for efficient extraction of organochlorine pesticides from water.
• Assess cartridge background and its impact on detection limits.
• Demonstrate analytical speed improvements using a GC Accelerator oven insert and hydrogen carrier gas.

Methodology

Water samples (100 mL) were spiked with 23 organochlorine compounds at 8–16 ppb (and separately 2–4 ppb) in 2 mL methanol and acidified with sodium sulfite (pH <2). CarboPrep Plus SPE cartridges (3 mL, 95 mg) were conditioned sequentially with ethyl acetate, dichloromethane, methanol, and deionized water. Samples were loaded at 10 mL/min under vacuum, dried for 10 min, then eluted with 25 mL ethyl acetate.

Instrumentation

The analytical setup included:

• Agilent 7890A GC equipped with dual micro-ECD detectors at 330 °C.
• GC Accelerator Oven Insert kit to reduce oven volume and enable high ramp rates.
• Two analytical columns in a “Y” configuration: Rtx-CLPesticides (30 m × 0.32 mm × 0.32 µm) and Rtx-CLPesticides2 (30 m × 0.32 mm × 0.25 µm), plus a 5 m guard column.
• Hydrogen carrier gas at constant flow (100 cm/sec) with nitrogen make-up gas.
• Topaz single-taper inlet liner with wool, splitless injection (2 µL).

Main Results and Discussion

SPE recoveries at 8–16 ppb averaged 86–93% (RSD <6%), demonstrating reliable extraction. At 2–4 ppb, slight losses of more volatile analytes were observed, indicating room for optimization in sample transfer. Fast GC, using the accelerator insert and hydrogen, separated all pesticides in ~5 minutes, with total cycle times near 10 minutes per sample. Cartridge blanks showed minimal background, supporting low detection limits.

Benefits and Practical Applications

Compared to traditional liquid–liquid extraction, the optimized SPE method offers:

• Significant solvent reduction and lower waste disposal costs.
• Reduced labor and hood space requirements.
• Higher sample throughput with consistent recoveries.
• Seamless integration with fast GC for rapid results.

Future Trends and Potential Uses

Further enhancements may include automated SPE workflows to minimize variability and improve low-level recoveries. Expanding fast GC methods with alternative detector technologies could broaden applicability to other semi-volatile contaminants. The combination of high-speed instrumentation and optimized extraction is poised to become standard in regulatory and research laboratories.

Conclusion

The study demonstrates that Resprep® CarboPrep Plus SPE cartridges, coupled with a GC Accelerator oven insert and hydrogen carrier, deliver a rapid, reliable, and cost-effective workflow for organochlorine pesticide analysis. Laboratories can achieve high throughput and meet stringent detection requirements while reducing solvent use and labor.

References

No formal literature references were provided in the original document.