Untargeted analysis with GC-Orbitrap: a powerful tool for the authentication of spices and herbs

Significance of the Topic

The authentication of spices and herbs is critical to ensure food safety and protect consumers from economic fraud. Oregano is especially susceptible to adulteration because visually similar leaves from cheaper plants can be mixed in undetected. A robust analytical workflow capable of profiling volatile organic compounds (VOCs) in complex herbal matrices provides quality control laboratories and food manufacturers with a reliable means to detect such adulteration and maintain product integrity.

Objective and Study Overview

This study demonstrates an untargeted workflow combining headspace solid-phase microextraction (HS-SPME) with high-resolution GC-Orbitrap mass spectrometry to differentiate authentic oregano from samples adulterated with closely related herbs. Native oregano and intentional blends containing thyme, marjoram, or olive leaves (10% w/w) were analyzed to identify unique marker compounds and quantify changes in aroma profiles. The approach emphasizes full-scan acquisition to enable retrospective data mining and comprehensive chemometric evaluation.

Used Instrumentation

• Thermo Scientific Orbitrap Exploris GC 240 mass spectrometer
• Thermo Scientific TriPlus RSH Autosampler with SPME Arrow
• Thermo Scientific TraceGOLD TG-1MS capillary column (30 m × 0.32 mm, 1.0 μm)
• Split/splitless Instant Connect injectors with SPME Arrow liners
• Data processing: Xcalibur, Compound Discoverer 3.2, Mass Frontier

Methodology

Herb samples were homogenized, weighed (150 mg) into 10 mL headspace vials, and extracted via HS-SPME Arrow (DVB/CWR/PDMS coating) at 60 °C for 15 minutes. Volatiles were desorbed in splitless mode and separated on a 30 m TG-1MS column under a temperature gradient from 40 °C to 300 °C. Mass spectra were acquired in full-scan electron ionization (EI, m/z 40–450) and positive chemical ionization (PCI, m/z 80–450) modes at 60,000 FWHM resolution. PCI adducts confirmed molecular formulas, while targeted MS/MS in the HCD cell supported structural assignments.

Results and Discussion

Full-scan EI chromatograms revealed distinctive peaks for native and adulterated oregano. Compounds such as α-pinene and camphene, predominating in thyme, were detected at elevated levels in oregano mixed with thyme. Carvacrol and thymol displayed contrasting abundance patterns between authentic oregano and adulterants. Chemometric analysis in Compound Discoverer included deconvolution, library matching (NIST17), retention index filtering, PCA, and volcano plots. PCA scores clearly segregated pure and adulterated groups. Volcano plots highlighted markers with significant fold changes: camphene (+7-fold), α-pinene (+3.6-fold) in thyme-adulterated samples; allyl furoate (+3.5-fold) in olive leaf blends; and methyl cinnamate (+2.5-fold) in marjoram mixtures. PCI data provided unambiguous molecular ion confirmation within 1 ppm mass error. MS/MS spectra generated key fragments that corroborated proposed formulas and facilitated confident identification.

Benefits and Practical Applications

• Minimal sample preparation and rapid headspace extraction streamline high-throughput testing.
• High-resolution full-scan acquisition enables both targeted compound quantification and non-targeted screening, including retrospective analysis.
• Integrated chemometric workflows quickly distinguish authentic herbs from fraudulent mixtures, supporting quality assurance and regulatory compliance.
• Accurate mass measurements and MS/MS structural elucidation increase confidence in marker identification.

Future Trends and Opportunities

Advancements in GC-HRMS instrumentation and data analytics will further enhance non-targeted screening capabilities. Integration with machine learning algorithms may automate adulteration detection and predict new fraud patterns. Miniaturized sampling techniques and mobile GC-MS platforms could enable on-site herb authentication. Expanding spectral libraries and combining orthogonal techniques such as isotope ratio analysis will strengthen the robustness of multi-modal authenticity workflows.

Conclusion

This study validates the use of GC-Orbitrap technology coupled with HS-SPME Arrow sampling for comprehensive profiling of oregano VOCs. The untargeted workflow effectively discriminates authentic samples from those adulterated with similar herbs, leveraging high-resolution full-scan data, accurate mass PCI confirmation, and MS/MS fragmentation for structural validation. The approach delivers a powerful tool for food quality control, capable of detecting subtle compositional changes and novel adulterants.

References

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2. Cavanna D. et al. Challenges in non‐targeted MS methods for food fraud analysis: a proposed harmonized validation workflow. Trends Food Sci Technol. 2018;80:223–241.
3. Díaz-Maroto M.C., Pérez-Coello M.S., Cabezudo M.D. HS‐SPME analysis of volatile components of spices. Chromatographia. 2002;55:729–735.