Field Sampling for Pesticides, Using Solid Phase Microextraction/Capillary GC

Importance of the Topic

Field sampling of pesticides using solid phase microextraction (SPME) addresses critical challenges in environmental monitoring by minimizing analyte degradation and eliminating the need to transport liquid samples. Traditional storage in glass or plastic containers often results in over 70% loss of semivolatile pesticides within 24 hours. A portable SPME field sampler enables direct extraction, stabilizes analytes on a polymeric fiber, and improves data reliability for remote sampling campaigns.

Objectives and Overview

The study evaluates the performance of a portable field sampler equipped with a 100 µm polydimethylsiloxane (PDMS) fiber for extracting chlorinated, organophosphorus, triazine, and other pesticides from water in situ. Key goals include assessing extraction efficiency, storage stability on the fiber for up to three days, and compar­ing analyte retention versus conventional sample containers.

Methodology

Samples of 4 mL pesticide-spiked water (25% NaCl, pH 8) were extracted by direct immersion of the SPME fiber under stirring. Extraction times of 20 to 30 minutes were tested to optimize precision and sensitivity. Desorption was performed thermally in a gas chromatograph injection port at 260 °C for 10 minutes. Analyte responses after storage on fiber at 4 °C and room temperature were compared to responses from freshly extracted samples and to analytes stored in water vials.

Instrumentation Used

• SPME Portable Field Sampler with 100 µm PDMS fiber (Cat. No. 504823)
• Gas Chromatograph with Meridian MDN-5 column (30 m × 0.25 mm × 0.25 µm)
• Ion Trap Mass Spectrometer (scan range m/z 45–450)

Key Results and Discussion

SPME fibers retained over 85% of target pesticides after three days at 4 °C, whereas water samples lost more than 70% within 24 hours. Mean analyte loss on fiber after 3 days was <15%, compared to >75% loss in stored water. Temperature reduction during storage further improved retention by a few percent. Chromatograms demonstrated clear detection of 16 pesticides at 10 ppb levels. Adjusting extraction time and ionic strength enhanced reproducibility and sensitivity for different pesticide classes.

Benefits and Practical Applications

• Solvent-free, in-field extraction reduces logistic complexity and waste.
• Enhanced analyte stability on fiber supports remote sampling without immediate lab access.
• Compatibility with GC/MS allows rapid, direct analysis with minimal background peaks.
• Single fiber chemistry (PDMS) can target a broad range of semivolatile pesticides.

Future Trends and Applications

Advancements may include development of novel fiber coatings for polar and low-boiling analytes, integration with portable GC/MS systems for on-site screening, and automated or robotic samplers for high-throughput field monitoring. Expansion to soil, air, and food matrices will broaden the utility of SPME in environmental and food safety applications.

Conclusion

The portable SPME field sampler with a 100 µm PDMS fiber offers a robust, efficient approach for pesticide sampling in remote locations. By stabilizing analytes directly on the fiber and reducing sample losses, this method enhances data quality and streamlines field operations compared to conventional container storage.

References

No specific literature references were provided in the original application note.