Extraction of PAHs from Urban Air Particulates Using Supercritical Fluids

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental contaminants originating from incomplete combustion processes. Accurate quantification of PAHs in urban air particulates is essential for assessing human exposure risks and guiding pollution control strategies.

Study Aims and Overview

This study evaluates a high‐temperature supercritical fluid extraction (SFE) approach for isolating PAHs from urban air particulate reference material (SRM 1649). The goal is to compare recoveries against certified values and benchmark conventional liquid/solid extraction methods.

Methodology and Instrumentation

Materials and extraction workflow:

• Sample: 0.5 g SRM 1649 urban air particulates
• Extraction vessel: 1 mL stainless steel cell
• Supercritical fluid: CO₂ at 600 bar, 180 °C, flow rate 2 L/min (gas equivalent)
• Extraction sequence: 10 min static phase, 30 min dynamic phase
• Collection: 1 g/6 mL C18 SPE cartridge
• SPE rinse: 5 mL pesticide‐grade methanol with internal standard

Used instrumentation:

• Applied Separations Spe‐ed SFE supercritical extraction system
• Gas chromatography–mass spectrometry (GC‐MS)

Results and Discussion

The high‐temperature SFE protocol provided PAH recoveries comparable to or exceeding certified values for key analytes such as phenanthrene, pyrene and benz(a)anthracene. Elevated temperature and pressure conditions improved desorption kinetics from weathered particulate surfaces, yielding more complete extraction than standard EPA liquid/solid techniques.

Practical Benefits and Applications

Key advantages of the optimized SFE method include:

• Reduced organic solvent consumption for greener analytical workflows
• Rapid extraction cycles supporting high laboratory throughput
• Enhanced recovery of low‐volatility, weathered PAHs
• Applicability in QA/QC, regulatory monitoring and industrial environmental analysis

Future Trends and Potential Applications

Ongoing developments may encompass integration of SFE with advanced detectors (e.g., tandem MS), adaptation to complex matrices (soils, sediments, biota), miniaturized and portable SFE platforms for field monitoring, and automated systems for real‐time environmental surveillance.

Conclusion

High‐temperature supercritical CO₂ extraction demonstrates a robust, efficient and environmentally friendly approach for PAH analysis in urban air particulates. The method achieves excellent recoveries, aligns well with reference standards, and supports comprehensive environmental risk assessment.