Trace analysis of Polycyclic Aromatic Hydrocarbons (PAHs) in water using Twister SBSE Technology

Significance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants with health hazards dependent on their molecular structure. Traditional extraction methods are time-consuming and prone to contamination. The adoption of stir bar sorptive extraction (SBSE) using Twister technology offers an advanced, automated approach for trace-level PAH analysis in water samples.

Objectives and Study Overview

This study aims to develop a fully automated gas chromatography–mass spectrometry (GC–MS) method for trace-level determination of 16 PAHs in water via Twister SBSE, improving efficiency and reducing solvent use compared to EPA Method 610.

Instrumentation

• Gerstel MultiPurpose Sampler (MPS) 2 XL
• Gerstel Thermal Desorption Unit (TDU)
• Gerstel Cooled Injection System (CIS) 4
• Agilent 7890A Gas Chromatograph with HP-5 column (30 m × 0.25 mm × 0.5 µm)
• Agilent 5975C Inert XL Mass Selective Detector
• Maestro software Version 1.4.8.14/3.5

Methodology

Water samples (100 mL) spiked with 16 PAHs (0.01–1.0 µg/L) containing 5% methanol were stirred with PDMS-coated Twister bars for 2 hours. After drying, Twisters were thermally desorbed in the TDU and focused in the CIS before transfer to the GC column. The GC program included a temperature gradient from 50°C to 310°C and single ion monitoring for each analyte.

Key Results and Discussion

• Linearity: Most PAHs showed strong calibration linearity (R² > 0.99) over 0.01–1.0 µg/L.
• Precision: Repeatability (n = 5) yielded RSD values below 10% for 13 PAHs; a few high-mass PAHs required further optimization.
• Detection: Trace-level detection down to 0.01 µg/L was demonstrated with clear SIM chromatograms for benzo(k)fluoranthene, benzo(b)fluoranthene, and benzo(a)pyrene.
• Limitations: Dibenz(ah)anthracene and benzo(ghi)perylene needed quadratic calibration models and improved desorption conditions.

Benefits and Practical Applications

The Twister SBSE–GC–MS method simplifies sample preparation by eliminating liquid–liquid extraction, reducing solvent consumption and risk of contamination. Automated desorption and injection improve throughput and reproducibility, making the approach suitable for routine environmental monitoring and QA/QC in water analysis.

Future Trends and Potential Applications

Further work will refine detection limits and precision across the full concentration range, validate recoveries in real water matrices, and develop industry performance criteria. SBSE could be expanded to other volatile and semi-volatile organic compounds in environmental and industrial samples.

Conclusion

Twister SBSE coupled with GC–MS provides a robust, automated, and solvent-free method for trace analysis of PAHs in water. The approach achieves high sensitivity, good linearity, and reproducibility, offering a valuable alternative to traditional extraction techniques.

References

• Maury A, Carrier D, Stubbs J. Trace analysis of PAHs in water using Twister SBSE technology. Chromatography Technical Note No AS 127; Anatune Ltd; 2012.