EA-IRMS: Tracing geographical origin of Argan oil using carbon and oxygen isotope fingerprints

Importance of the topic

Argan oil is a premium, geographically protected product with high social and economic importance in Morocco. Ensuring its authenticity and tracing its origin are vital to protect consumers, uphold producer reputation and prevent economically motivated fraud.

Objectives and Study Overview

This study explores how combined carbon (δ13C) and oxygen (δ18O) isotope fingerprints of Argan oil can differentiate its geographical origin within Morocco. By analyzing 47 samples from multiple regions, the research aims to establish a robust isotopic framework for provenance verification.

Methodology and Instrumentation

Samples were prepared by weighing 0.3 mg of oil into tin capsules for carbon analysis and 0.6 µL into silver capsules for oxygen analysis. Carbon isotopes were measured via combustion at ~1020 ˚C, while oxygen isotopes were determined by pyrolysis at ~1450 ˚C. Both gases were separated chromatographically and analyzed by Isotope Ratio Mass Spectrometry in under 600 seconds per analysis.

Used Instrumentation

• Thermo Scientific EA IsoLink IRMS System
• MAS Plus Autosampler
• Combustion reactor (for δ13C) and pyrolysis reactor (for δ18O)
• Isotope Ratio Mass Spectrometer (IRMS)

Key Results and Discussion

Lower δ18O values were found in samples from the Essaouira and Chtouka regions, while higher δ18O corresponded to oils from high-altitude areas. Coastal, humid regions (Essaouira, Agadir) yielded more negative δ13C values, reflecting photosynthetic responses to moisture. Multi-isotope plots of δ13C versus δ18O revealed clear clustering by region, indicating that local rainfall patterns, altitude, temperature and shoreline proximity govern the isotopic signatures.

Benefits and Practical Applications

The established isotopic method provides a reliable tool for regulatory bodies and commercial laboratories to verify Argan oil provenance. It helps detect adulteration, supports protected designation compliance and enhances consumer confidence in product authenticity.

Future Trends and Opportunities

Expanding the database with additional regional samples and incorporating hydrogen isotopes could further refine geographical discrimination. Integration of chemometric modeling and machine learning may automate origin prediction. The approach can be extended to other protected agricultural products for comprehensive food authentication.

Conclusion

Carbon and oxygen isotope analysis by EA-IRMS effectively differentiates Argan oil from distinct Moroccan regions. This technique offers a scientifically robust, high-throughput solution for provenance verification and fraud prevention.

References

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2. Camin F, Bontempo L, Ziller L, Piangiolino C, Morchio G (2010) Rapid Communications in Mass Spectrometry 24(12).
3. Dansgaard W (1964) Tellus 16.