Automated Solid Phase Extraction of PAH Compounds Utilizing the SPE-DEX 5000

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants in water requiring sensitive extraction and analysis to ensure compliance with regulatory limits and to assess contamination levels in drinking water, surface water, groundwater and wastewater.

Objectives and Study Overview

This study evaluates the performance of automated disk SPE using the SPE-DEX 5000 system to extract a range of 16 priority PAH compounds at mid-level spiking (50 µg/L) from reagent and pond water. Three sorbent media—C18 high-capacity silica, divinylbenzene (DVB) polymer, and hydrophilic-lipophilic balanced (HLB) polymer—are compared in terms of recovery, precision, and suitability for particulate-laden matrices using standard disk holders and a Fast Flow disk holder with prefilters.

Methodology and Instrumentation

The automated workflow comprises: conditioning of 47 mm SPE disks with organic solvents and acidified water; sample loading at controlled flow rates; disk drying; stepwise elution with acetone and methylene chloride; and automated concentration to ~0.9 mL using the DryVap concentrator. Final extracts are adjusted to 1.0 mL, spiked with internal standard, and analyzed by GC/MS (Agilent 6890/5975C) on a ZB SemiVolatiles column. Instrumentation includes the SPE-DEX 5000 extractor, DryVap system, Atlantic C18 HC, DVB and HLB-M disks, Fast Flow holders with 1 µm and 5 µm prefilters, and a GC/MS setup.

Main Results and Discussion

Reagent water spikes yielded average recoveries above 83% for all media, with naphthalene as the lowest at ~69–77%. Precision across three replicates was within 4% RSD, with HLB-M showing the best reproducibility. Pond water matrix spikes exhibited similar recoveries and RPD values below 6% for HLB-M, indicating robust performance in particulate samples. Method blanks were below detection (<0.5 µg/L) across all disks, confirming minimal background.

Benefits and Practical Applications of the Method

The automated disk SPE approach eliminates emulsion issues inherent to liquid-liquid extraction, reduces solvent consumption and evaporation time, and allows customizable sorbent selection to match analyte polarity. Disk formats support large-volume and particulate-rich water samples with minimal clogging. Automation on the SPE-DEX 5000 improves inter-operator precision and frees analyst time while delivering consistent recoveries for routine environmental monitoring per EPA methods.

Future Trends and Opportunities

Emerging developments may include integration of online SPE-GC/MS workflows, further miniaturization and green solvent use, expansion to additional polar and transformation products, and incorporation of real-time monitoring sensors. Advances in novel sorbent chemistries and combined SPE-LC/GC platforms could streamline multi-class contaminant analysis in complex environmental matrices.

Conclusion

The SPE-DEX 5000 automated disk SPE system coupled with C18, DVB and HLB-M disks provides reliable, high-throughput extraction of PAHs from diverse water samples. With recoveries above 70% and excellent precision, the method conforms to EPA 8270 requirements, offering a robust solution for environmental laboratories focused on quality, efficiency, and regulatory compliance.

References

• US EPA Method 8270E: Semivolatile Organic Compounds by GC/MS
• US EPA Method 8000D: Determination of Organic Compounds by GC/MS