Fast Screening of Water and Soil Samples, Using Solid Phase Microextraction (SPME)

Importance of the Topic

Rapid and reliable screening of volatile organic compounds in environmental samples is essential for regulatory compliance, risk assessment and timely decision making in water and soil monitoring programs. Solid phase microextraction (SPME) offers a solvent-free, fast and cost-effective alternative to traditional purge and trap methods, minimizing sample preparation time and reducing potential contamination.

Objectives and Study Overview

This report describes the implementation of an SPME-GC/FID screening procedure at Lancaster Laboratories for routine analysis of water and soil samples. The main goals were to achieve:

• Fast sample throughput of at least 80–90 analyses per shift
• Accurate semiquantitative assessment of a wide range of aromatic, halogenated and aliphatic VOCs
• Compatibility with existing GC instrumentation and ease of automation

Methodology and Used Instrumentation

The screening workflow uses headspace SPME with no stirring, followed by direct thermal desorption into a gas chromatograph with flame ionization detection. Key parameters include:

• SPME fiber: 30 µm polydimethylsiloxane
• Sampler: Varian 8200CX SPME AutoSampler (or manual holder)
• GC column: 10 m × 0.20 mm ID SPB-1, 1.2 µm film
• Carrier gas: hydrogen at 12 psi with make-up nitrogen
• Extraction: 12 s headspace at ambient temperature, 0.7 mL sample with NaCl
• Desorption: 2–3 min at 250 °C in a 0.75–1.0 mm injector liner
• Oven program: 70 °C (0.2 min) to 180 °C at 50 °C/min
• Detection: FID at 250 °C

Main Results and Discussion

The optimized SPME method characterizes a broad range of VOCs in under 2½ minutes per sample. Comparison with established purge and trap/GC methods in water and soil matrices showed good agreement (91–125% for benzene, toluene, ethylbenzene, xylenes). No significant carryover was observed, and the system maintained linear response across typical regulatory concentration ranges.

Benefits and Practical Applications

SPME screening reduces analysis time by at least 30 minutes for high-level VOC samples and prevents system overload in downstream confirmatory analyses. The solvent-free approach lowers operating costs and simplifies instrument maintenance. Laboratories can reliably prescreen environmental samples to prioritize full quantitative analysis and improve overall workflow efficiency.

Future Trends and Applications

Advances in fiber coatings and automated SPME interfaces can further expand the range of detectable compounds and improve sensitivity. Integration with mass spectrometric detectors and miniaturized portable systems promises on-site environmental monitoring. Development of novel sorbent phases may enable combined analysis of semi-volatile organics and polar contaminants.

Conclusion

The described SPME-GC/FID screening method at Lancaster Laboratories demonstrates a robust, high-throughput solution for rapid VOC assessment in water and soil. Its ease of use, minimal carryover, and compatibility with existing GC platforms make it an attractive prescreening tool for environmental and regulatory laboratories.

References

• Schumacher T.L. Fast Screening of Water and Soil Samples Using Solid Phase Microextraction (SPME). The Supelco Reporter, Vol. 16, No. 1, 1997. Reprinted by Sigma-Aldrich Co.