New Applications for SPME/Capillary GC: Screening for Amphetamines in Urine; Identifying Tobacco Varieties; Monitoring Nitrogen-Containing Herbicides in Water

Significance of the Topic

Solid Phase Microextraction (SPME) has become a transformative sample preparation technique in analytical chemistry due to its solvent free operation, integration with capillary gas chromatography, rapid processing time, and enhanced sensitivity. It supports trace level analyses in biological fluids, food matrices, and environmental samples while reducing hazards and cost of conventional extraction methods.

Objectives and Study Overview

This summary covers three separate studies demonstrating new applications of SPME coupled to capillary GC:

• Screening methamphetamine and amphetamine in urine headspace
• Characterizing tobacco varietal headspace profiles
• Monitoring nitrogen containing herbicides in water

Methodology

Each study employed a tailored SPME protocol. For amphetamine screening, a buffered urine aliquot was heated with added salt at 80 C, and a polydimethylsiloxane fiber sampled the headspace prior to GC injection. Tobacco samples were adjusted to controlled moisture, mixed with KCl solution, heated at 95 C, and similarly headspace extracted. Water samples were acidified or salted and gently stirred while immersed with a polyacrylate fiber for up to 50 minutes at ambient temperature.

Instrumentation Used

Key components included:

• SPME fibers coated with polydimethylsiloxane or polyacrylate
• Capillary GC columns (polydimethylsiloxane and phenylmethylsiloxane phases)
• Detectors such as flame ionization, nitrogen phosphorus, and mass spectrometric ion trap
• Sample heating blocks and autosampler modifications for automated SPME

Main Results and Discussion

Heated headspace SPME achieved a 20 fold sensitivity gain for methamphetamine and amphetamine relative to conventional headspace sampling, with excellent linearity (r2 > 0.99) and precision under 7 percent. Tobacco headspace fingerprints allowed clear discrimination among twelve varieties by comparing characteristic volatile markers. In water monitoring of 22 nitrogen containing herbicides, SPME GC MS outperformed EPA Method 507 508, attaining sub nanogram per liter detection for many analytes and reproducibility within 2 to 20 percent.

Benefits and Practical Applications

The reported SPME methods offer:

• Rapid, simple sample preparation without organic solvents
• Enhanced sensitivity and selectivity for trace compounds
• Reduced interference in forensic and environmental analyses
• Fast screening workflows for legal, agricultural, and quality control settings

Future Trends and Potential Applications

Advancements may include new selective fiber coatings, broader automation integration, coupling with high resolution mass spectrometry, and expanded use in metabolomics, food authenticity testing, and continuous environmental monitoring.

Conclusion

SPME coupled with capillary GC delivers versatile, efficient, and high sensitivity approaches for a wide range of analytical challenges. The studies highlighted confirm its value for forensic screening, varietal profiling, and trace pesticide analysis, demonstrating strong potential for future method development and field deployment.

References

1. Yashiki M Kojima Miyazaki Nagasawa Iwasaki and Hara Detection of Amphetamines in Urine Using Head Space Solid Phase Microextraction and Chemical Ionization Selected Ion Monitoring Forensic Science International in press 1995
2. Hara Nagata and Kimura Z Rechtsmed 96 93 104 1986
3. Olsen Gullikssen and Christophersen Clin Chem 38 611 612 1992
4. Boyd Boland and Pawliszyn Manuscript submitted to Analytical Chemistry 1995