A Guide to Preparing and Analyzing Chlorinated Pesticides

Significance of the Topic

Analysis of chlorinated pesticides and PCBs is fundamental in environmental laboratories because these compounds are persistent, bioaccumulative and subject to strict regulatory limits. Robust methods are needed to handle complex matrices, minimize interferences and maintain instrument performance over long sequences.

Objectives and Study Overview

This guide consolidates U.S. EPA methods 3510, 3520, 3535, 3545, 3560, 3640, 3660, 3665, 8081, 8082 and 608 for the preparation and analysis of chlorinated pesticides and PCBs in water, soil and biota samples. It compares extraction techniques, details cleanup strategies and demonstrates optimized GC injection modes and column selections to improve throughput and data quality.

Methodology and Instrumentation Used

Extraction approaches evaluated include:

• Liquid–liquid extraction by separatory funnel (EPA 3510) and automated systems (EPA 3520)
• Solid-phase extraction (EPA 3535) for aqueous matrices
• Soxhlet and ultrasonic extraction for soils and biota
• Pressurized fluid extraction (EPA 3545) and microwave-assisted extraction
• Supercritical fluid extraction (EPA 3560) for solvent-reduced workflows

Cleanup procedures focus on:

• Gel permeation chromatography (EPA 3640) to remove lipids and sulfur
• Florisil®, silica and graphitized carbon SPE (EPA 3620B, 3630C) for polar and nonpolar co-extractants
• Sulfuric acid digestion (EPA 3665) for unsaturated and aromatic contaminants in PCB-only workflows
• Activated mercury or copper cleanup for residual sulfur

Instrumentation Used

• Preparative GPC system with calibrated retention bands
• Automated liquid–liquid extractors (conventional and accelerated types)
• Gas chromatograph equipped with electron capture detector
• Rtx®-CLPesticides and Rtx®-CLPesticides 2 GC columns
• Split/splitless, direct and cold on-column inlet configurations with deactivated liners

Main Results and Discussion

• Consistent pH adjustment and controlled extraction shaking ensure quantitative recovery in liquid–liquid methods.
• Granular sodium sulfate drying prevents water carryover and analyte loss during concentration.
• GPC provides the most effective lipid and sulfur removal for soil and biota extracts, though at higher cost and longer processing times.
• SPE cleanup with Florisil®, silica and graphitized carbon tubes offers fast turnaround for low-contamination samples; graphitized carbon effectively retains nonpolar interferences but requires validation of elution volumes.
• Sulfuric acid cleanup eliminates unsaturated interferences but is limited to PCB analysis due to pesticide reactivity.
• Direct injection with deactivated liners minimizes pesticide breakdown; split/splitless and on-column modes each have optimal use cases depending on matrix cleanliness.
• Rtx®-CLPesticides column pair provides baseline resolution of 22 common chlorinated pesticides in under 25 minutes, with a maximum operating temperature of 330 °C and compatibility with helium or hydrogen carrier gas.

Benefits and Practical Applications of the Method

Implementation of these optimized workflows reduces instrument maintenance, improves detection limits and shortens calibration sequences. The unified column pair simplifies dual-column confirmation analyses and permits a single calibration mix, freeing laboratory time and increasing sample throughput.

Future Trends and Potential Applications

Advances in automated extraction and cleanup, including membrane-based accelerated liquid–liquid systems and enhanced SPE sorbents, will further streamline workflows. Continued development of inert inlet materials and high-temperature GC phases will support analysis of more challenging high–molecular-weight contaminants. Integration with mass spectrometric detection is likely to expand selectivity and lower reporting limits for emerging organochlorine pollutants.

Conclusion

A strategic combination of proven extraction protocols, targeted cleanup steps and specialized GC columns delivers reliable, high-throughput analysis of chlorinated pesticides and PCBs. Adhering to EPA guidance while adopting advanced chemistries ensures compliance, enhances data quality and reduces operational costs.

References

• Journal of AOAC International, Vol. 49, No. 6, 1966, pp. 208–223
• US EPA SW-846 Test Methods for Evaluating Solid Waste Physical/Chemical Methods, Third Edition Update III, 1996
• US EPA Contract Laboratory Program Statement of Work for Organic Analysis 0LM04.0, Exhibit D Pesticides/Aroclors