INTRODUCTION TO SPME AND SPME–TRAP

Significance of SPME and SPME–trap

Solid-phase microextraction (SPME) and its extension SPME–trap have become essential tools for rapid, solvent-free sampling of volatile and semi-volatile compounds. Their ability to concentrate analytes directly from solids, liquids, or headspace simplifies sample preparation, reduces solvent waste, and enhances sensitivity in environmental, food, and clinical analysis.

Objectives and Overview

This article introduces the principles of SPME and the development of the SPME–trap approach. Key goals include summarizing the historical evolution of the technique, describing typical workflows, and highlighting applications where enhanced preconcentration and peak shape improvement are critical.

Methodology and Instrumentation

The SPME process employs a thin, sorbent-coated fiber (10–20 mm length, coating thickness 20–100 µm, sorbent volume ~0.5 µL) housed in a guiding needle. Extraction can be performed either immersively (fiber submerged in liquid) or in headspace mode (fiber exposed above sample). Analytes equilibrate between the sample matrix and the sorptive phase via adsorption or absorption depending on coating type. Desorption occurs thermally into a gas chromatograph inlet or into a sorbent-packed focusing trap for improved sensitivity.

Instrumentation

• SPME fibers with polymeric or solid coatings (eg liquid-like films versus porous adsorbents)
• GC–MS systems equipped with standard injector ports
• Preconcentration traps for sorbent-packed focusing and backflush injection
• Automated autosamplers compatible with both SPME and SPME–trap modules (eg Centri multi-mode platform)

Main Results and Discussion

SPME–trap coupling significantly sharpens chromatographic peaks by forming narrow analyte bands in the focusing trap prior to GC analysis. Compared to direct desorption, this approach enhances sensitivity, especially for low-abundance compounds, and mitigates issues related to splitless injection. Historical milestones include the first fiber desorption in 1987, commercial SPME–GC systems by 1993, robust polymer fibers in 1998, and multi-mode autosamplers launching in the 2000s.

Benefits and Practical Applications

• Fast, solvent-free sample preparation with minimal water interference
• Wide applicability to aroma profiling in food, pollutant monitoring in soil and water, and biomarker analysis in clinical samples
• Automated, high-throughput workflows with flexible split flows for dynamic range control
• Improved peak resolution and sensitivity through sorbent-packed trapping
• Low per-sample cost and reusable fibers

Future Trends and Opportunities

Advances in fiber materials, such as superelastic metal-core designs and larger volume SPME Arrow formats, will further boost capacity and robustness. Integration with multi-mode platforms promises streamlined workflows combining SPME, thermal desorption, and headspace sampling. Emerging applications in real-time environmental monitoring, point-of-care clinical diagnostics, and in situ flavor analysis are likely to expand the technique’s impact.

Conclusion

SPME and SPME–trap offer versatile, sensitive, and automatable solutions for the extraction and analysis of VOCs and SVOCs across diverse matrices. Continued innovation in fiber technology and instrument integration will further enhance their role in analytical chemistry, supporting rigorous quality control and research across industries.