Untargeted Analysis with GC-Orbitrap: A Powerful Tool for the Authentication of Spices and Herbs

Importance of the Topic

Adulteration of culinary herbs like oregano poses significant risks to food quality, safety and consumer trust. Non-targeted analytical strategies that can detect undeclared plant material are critical for quality control in the food industry. High-resolution mass spectrometry combined with robust data processing enables comprehensive profiling of volatile compounds and reliable authentication of spices and herbs.

Objectives and Study Overview

This study evaluates an untargeted workflow using GC-Orbitrap technology and headspace SPME Arrow sampling to detect and characterize adulteration in oregano. Authentic oregano samples were intentionally adulterated at 10% with thyme, marjoram and olive leaves. The goal was to identify unique marker compounds and statistically distinguish authentic and fraudulent samples through full-scan analysis, multivariate statistics and high-accuracy MS/MS confirmation.

Methodology

• Sample Preparation: Native oregano mixed with 10% adulterants (thyme, marjoram, olive leaves); homogenized and analyzed in triplicate.
• Headspace Extraction: DVB/CWR/PDMS SPME Arrow for volatile capture, minimal sample preparation.
• GC-MS Acquisition: Orbitrap Exploris GC 240 operated in electron ionization (EI) at 60 000 FWHM and positive chemical ionization (PCI) modes; full-scan data for untargeted screening; PCI-MS/MS for structural confirmation.
• Data Processing: Thermo Scientific Xcalibur for acquisition; Compound Discoverer 3.2 for deconvolution, library matching (NIST 2020), retention index calculation and multivariate analysis (PCA, volcano plots); Mass Frontier 8.0 for predictive fragmentation and structural assignment.

Instrumentation Used

• Thermo Scientific Orbitrap Exploris GC 240 system with Instant Connect Split/Splitless injectors.
• Thermo Scientific TriPlus RSH autosampler with SPME Arrow configuration.
• Thermo Scientific TraceGOLD TG-1MS capillary column (30 m × 0.32 mm × 1.0 μm).

Main Results and Discussion

Multivariate analysis revealed clear separation between authentic and adulterated oregano. In oregano spiked with thyme, camphene and α-pinene increased by approx. 7-fold and 3-fold respectively. Adulteration with olive leaves elevated allyl furoate by 3.5-fold, while marjoram introduced methyl cinnamate with a log2-fold change of 2.5. High-accuracy PCI-MS/MS (sub-1 ppm mass error) confirmed molecular formulas and provided structural information for key markers. Volcano plots efficiently highlighted statistically significant changes in volatile profiles.

Benefits and Practical Applications

• Single-step sampling and untargeted full-scan acquisition enable retrospective data analysis and rapid screening.
• High resolving power and mass accuracy support confident identification of unknown compounds.
• Statistical workflows (PCA, volcano plots) facilitate fast discrimination of authentic versus adulterated samples.
• Streamlined software tools reduce time to result and improve data clarity for QA/QC laboratories.

Future Trends and Potential Applications

Analytical advances may include expanded spectral libraries, machine learning for pattern recognition, miniaturized high-resolution MS systems for on-site testing and integration with metabolomics platforms. Such developments will broaden untargeted screening to diverse food matrices and enhance supply-chain integrity.

Conclusion

The GC-Orbitrap untargeted workflow combining headspace SPME Arrow sampling and advanced data analysis represents a powerful approach for spice authentication. Its high sensitivity, accuracy and comprehensive statistical evaluation deliver reliable detection of low-level adulterants, offering a valuable tool for food quality control.

References

• Riccardino G, Roberts D, Zheng X, Cole J, Dolata L, Cojocariu C. Untargeted Analysis with GC-Orbitrap: A Powerful Tool for the Authentication of Spices and Herbs. Thermo Fisher Scientific; 2021.