Robustness of SPME Arrow Immersion Sampling: Polycyclic Aromatic Hydrocarbons in Drinking Water

Significance of the Topic

The determination of polycyclic aromatic hydrocarbons (PAHs) in drinking water is critical due to their toxic and carcinogenic properties.
Immersion sampling using solid-phase microextraction (SPME) Arrow offers a solvent-free, rapid, and automated approach to extract trace PAHs from complex water matrices, including hard water with high mineral content and treated with sodium thiosulfate.

Objectives and Study Overview

This study aimed to assess the repeatability and robustness of an automated PDMS SPME Arrow immersion method coupled to GC–MS for quantifying 16 PAHs in tap water.
The specific goals included evaluating the durability of a single SPME Arrow over 100 sequential injections and optimizing the automated workflow.

Methodology and Instrumentation

• Sample preparation: 15 mL of spiked drinking water (250 mg/L minerals) in 20 mL vials, treated with 90 µL of 1.8% sodium thiosulfate to quench residual chlorine.
• Automated SPME Arrow workflow: vortex mixing, agitation at 35 °C, immersion extraction (30 min) with 1500 rpm stirring, followed by desorption in the GC inlet (5 min), intensive wash and conditioning cycles.
• Instrumentation: PAL RTC 120 autosampler with a 1.1 mm × 100 µm PDMS SPME Arrow; Shimadzu GC-2010 with Restek Rtx-i5 MS column; GCMS-QP2010 in EI mode with SIM acquisition.

Main Results and Discussion

• Repeatability: relative standard deviations (%RSD) for 100 injections ranged from 1.74% to 10.93% across all analytes, meeting robustness criteria.
• Durability: peak area ratios of the 100th to 1st injection ranged from 0.600 to 0.947, demonstrating the SPME Arrow maintained extraction efficiency over 100 uses.
• Workflow efficiency: the fully automated protocol minimized manual handling and ensured consistent cleaning to prevent mineral buildup.

Benefits and Practical Applications

• High throughput: automated sampling and cleaning cycles enable analysis of large sample sets with minimal operator intervention.
• Sustainable and cost-effective: solvent-free extraction reduces chemical usage and waste generation.
• Analytical robustness: reliable quantification of trace PAHs in challenging water matrices supports compliance monitoring and quality control.

Future Trends and Applications

Advancements in SPME Arrow coatings may further improve sensitivity and selectivity for emerging contaminants.
Integration with high-resolution mass spectrometry could enable non-target screening alongside targeted quantification.
Portable or field-deployable SPME Arrow systems may expand on-site water quality monitoring capabilities.

Conclusion

The automated PDMS SPME Arrow immersion method coupled with GC–MS demonstrates excellent repeatability and durability for PAH analysis in drinking water.
This workflow enhances throughput, ensures consistent performance over extended injection series, and supports sustainable laboratory operations.

References

• Emanuel Coelho, Célia Ferreira and Cristina M. M. Almeida, Analysis of Polynuclear Aromatic Hydrocarbons by SPME-GC-FID in Environmental and Tap Waters, Journal of the Brazilian Chemical Society, 19(6), 1084–1097, 2008.
• Andreas Kremser, Maik A. Jochmann and Torsten C. Schmidt, PAL SPME Arrow—Evaluation of a Novel Solid-Phase Microextraction Device for Freely Dissolved PAHs in Water, Analytical and Bioanalytical Chemistry, 408:943–952, 2016.