Analysis of Wastewater Samples using Disk Solid Phase Extraction (SPE) following US EPA Method 608.3

Significance of the Topic

Pesticide residues in wastewater pose risks to human health and the environment. Monitoring these contaminants is vital for regulatory compliance and ecosystem protection. Automated disk solid phase extraction aligned with US EPA Method 608.3 offers reliable, sensitive sample preparation for organochlorine pesticides and PCBs in diverse water matrices.

Study Objectives and Overview

This work evaluated automated disk SPE on reagent water, synthetic wastewater, and POTW influent following EPA Method 608.3. It compared conventional methylene chloride elution with solvent exchange versus direct hexane elution and assessed recovery, precision, and workflow efficiency.

Methodology and Instrumentation

• SPE-DEX 5000 system with Atlantic C18 disks and Fast Flow holder featuring 1 and 5 micrometer prefilters
• Automated disk conditioning, sample loading, wash, and elution protocols
• DryDisk-R membrane drying and DryVap in-line evaporation for extract concentration
• GC with dual micro electron capture detectors on an Agilent 6890 instrument
• Calibration range 0.5 to 200 micrograms per liter, surrogate spikes, and QC per EPA Method 608.3

Main Results and Discussion

Reagent and synthetic wastewater spikes achieved recoveries within the 25 to 160 percent window specified by EPA 608.3 and relative percent differences below 5 percent. Direct hexane elution matched performance of methylene chloride workflows, eliminating solvent exchange without loss of data quality. POTW influent tests also met acceptance criteria, though matrix variability affected trans-chlordane precision in one replicate, highlighting the influence of particulate load and prefilter selection.

Benefits and Practical Applications

• Automation improves reproducibility and minimizes user variability
• Direct hexane elution streamlines operations by removing solvent exchange steps
• Higher throughput and lower solvent consumption reduce costs
• Suitable for routine environmental monitoring and wastewater treatment plant compliance

Future Trends and Potential Applications

Advancements may include broader analyte coverage, integration with on-line cleanup and detection, development of greener elution solvents, and portable field-deployable SPE units. Further studies on surrogate behavior in hydrophobic matrices will enhance method robustness.

Conclusion

Automated disk SPE following EPA Method 608.3 delivers consistent recovery and precision for pesticide analysis across water matrices. Direct hexane elution simplifies sample preparation and supports efficient, compliant workflows in environmental laboratories.

References

• North Carolina State University. Some pesticides linked to respiratory wheeze in farmers. ScienceDaily. August 3 2016.
• US EPA. Method 608 ATP 3M0222 Alternative Test Procedure for measurement of organochlorine pesticides and PCBs in wastewater. Federal Register Vol 60 No 148 August 2 1995.
• ASTM. Standard Practice for the Preparation of Substitute Wastewater D5905 reapproved 2013.