Trace Detection of Fenthion in Olive Oil

Importance of the Topic

Olive oil is a dietary staple worldwide but can become contaminated with residual pesticides such as fenthion. Fenthion is restricted due to its moderate human toxicity and high toxicity to non‐target species. Monitoring trace levels of fenthion in olive oil ensures compliance with regulatory limits, protects consumer health, and prevents environmental impact.

Objectives and Study Overview

This application note demonstrates a rapid, on-site method for detecting trace fenthion residues in olive oil. Using Metrohm’s portable MISA system coupled with surface‐enhanced Raman spectroscopy (SERS) and gold nanoparticles, the study aims to validate a simple extraction and measurement protocol capable of identifying fenthion down to regulated limits.

Methodology

The procedure involves spiking olive oil with known fenthion concentrations (500 ng/mL to 100 μg/mL), performing liquid–liquid extraction with cyclohexane and acetonitrile, followed by phase separation. The extract is evaporated, reconstituted with gold nanoparticle colloid and salt, then measured by SERS. Key acquisition settings include 5 s integration time, 10 averages, and activated raster scanning to enhance signal uniformity.

Key Results and Discussion

Baseline‐corrected SERS spectra reveal clear fenthion signals down to 500 ng/mL. At low analyte levels, substrate‐derived peaks overlap with target signals; peak assignment via MISA Cal libraries enables differentiation. An inverse relationship between fenthion peak intensity and nanoparticle background confirms successful extraction and detection of the insecticide at sub‐μg/mL concentrations.

Benefits and Practical Applications

• Rapid, field‐deployable detection without large laboratory infrastructure.
• Simple sample preparation using common solvents and consumables.
• High sensitivity meets or exceeds regulatory limits for olive oil.
• Automated workflows and built‐in spectral libraries simplify operation.

Instrumentation

• Metrohm Instant SERS Analyzer (MISA Advanced, firmware 0.9.33, software MISA Cal V1.0.15)
• Gold nanoparticle ID Kit (ID Kit – Au NP, code 6.07506.440)
• MISA vial and P‐SERS attachments
• Cyclohexane, acetonitrile, NaCl solution (3 g/100 mL)

Future Trends and Potential Uses

Advances in nanoparticle substrates and machine‐learning‐driven spectral interpretation will further improve sensitivity and selectivity. Integration with mobile networks and cloud databases could enable real‐time monitoring of multiple contaminants in various food matrices. Expanding SERS libraries to cover diverse pesticides and adulterants will broaden field applications.

Conclusion

The MISA SERS approach offers a robust, user‐friendly solution for trace fenthion detection in olive oil, achieving regulatory compliance with minimal equipment. Its portability, ease of use, and rapid results make it ideal for on‐site quality control and environmental monitoring.