A comprehensive strategy for confident detection of oregano adulteration by GC-Orbitrap mass spectrometry

Significance of the topic

Oregano is a widely used culinary herb valued for its aroma and flavor. However, high market demand and price differences encourage adulteration with visually similar plant materials. Reliable detection methods are critical to ensure consumer safety, maintain product quality, and protect brand integrity.

Objectives and study overview

This study aimed to develop a robust strategy for detecting oregano adulteration using high-resolution GC-Orbitrap mass spectrometry combined with solid-phase microextraction. Two commercial oregano samples were profiled to identify volatile markers indicating the presence of unauthorized additives.

Methodology and instrumentation

Sample preparation involved headspace solid-phase microextraction with an SPME Arrow fiber coated with DVB/CWR/PDMS. Volatile compounds were separated on a TraceGOLD TG-1MS column and analyzed by an Exactive GC Orbitrap mass spectrometer in full-scan mode (50–550 Da) at 60,000 resolving power. Compound Discoverer software performed spectral deconvolution, library matching against NIST17, retention index filtering, and multivariate statistics. PCI experiments confirmed molecular ion assignments via characteristic adducts.

Main findings and discussion

Principal Component Analysis clearly separated the two oregano samples based on their volatile profiles. Sample 1 showed predominance of carvacrol, while sample 2 was rich in thymol. Volcano plots highlighted significant differences, identifying thymol methyl ether—common in coriander and thyme oils—exclusively in sample 2, suggesting intentional adulteration.

Benefits and practical applications

• High mass accuracy (<1 ppm) and resolving power enable detection of compounds across a wide concentration range.
• Integrated HS-SPME Arrow workflow simplifies sample preparation and enhances throughput.
• Compound Discoverer facilitates automated deconvolution, identification, and statistical interpretation.
• PCI confirmation provides unambiguous molecular ion verification.

Future trends and potential applications

Advances may include expanded spectral libraries and retention index databases, integration of multi-omics approaches, and automation for high-throughput screening. The methodology could be extended to other herbs and spices to safeguard food authenticity on a broader scale.

Conclusion

The combination of HS-SPME Arrow extraction, GC-Orbitrap high-resolution MS, and advanced data processing constitutes a powerful tool for oregano authenticity testing. This workflow delivers confident detection of fraudulent additives, supporting quality control in food production and research.

Used Instrumentation

• Thermo Scientific Exactive GC Orbitrap GC-MS
• Thermo Scientific TriPlus RSH autosampler with SPME Arrow
• TraceGOLD TG-1MS capillary column (30 m × 0.32 mm × 1.0 μm)
• Compound Discoverer 3.1 and TraceFinder software

References

1. Díaz-Maroto M.C., Pérez-Coello M.S., Cabezudo M.D. Headspace solid-phase microextraction analysis of volatile components of species. Chromatographia. 55 (2002):729–735.
2. Dubrabova L. et al. Food fraud in oregano: pesticide residues as adulteration markers. Food Chemistry. 276 (2019):726–734.