Essential Oil Metabolomic Profiling with HRMS and a Variety of Complementary Ionization Techniques - Allowing Discrimination of Samples of Different Botanical Origin and Non-Conformity

Importance of the Topic

Essential oils such as vetiver play a crucial role in perfumery and flavor industries due to their unique aromatic profiles. Traditional GC-MS methods focus on volatile compounds, but regulatory requirements and adulteration concerns necessitate comprehensive analysis of semi-volatile and non-volatile constituents.

Study Objectives and Overview

This study presents an untargeted metabolomic workflow that integrates UPLC, supercritical fluid chromatography (UPC²), multiple ionization sources (ESI, APCI, ASAP), and high-resolution MS (HRMS) to profile vetiver essential oils from Haiti, Indonesia, and Paraguay. The aim is to discriminate botanical origins and detect non-volatile adulterants in non-conforming batches.

Methodology

• Sample preparation: Dilution (1:10) of oil in MeOH:ACN 50:50, with QC mixtures included.
• UPLC-MS: ACQUITY UPLC I-Class, CORTECS C18 column, 5–99% MeOH:ACN gradient with 5 mM ammonium formate and 0.1% formic acid, ESI+/- at low/high voltages, MS^E acquisition (50–1200 m/z).
• UPC²-MS: ACQUITY UPC², Viridis HSS C18 SB column, supercritical CO₂/MeOH:ACN gradient, APCI ionization with variable corona current.
• Rapid screening: Atmospheric Solids Analysis Probe (ASAP) for 5-min fingerprinting.

Used Instrumentation

• Xevo G2-TOF Mass Spectrometer
• ACQUITY UPLC I-Class System
• ACQUITY UPC² System
• Viridis HSS C18 SB & CORTECS C18 Columns
• Progenesis QI & EZinfo Software
• MassLynx Software

Main Results and Discussion

• A total of 180 LC-MS/MS analyses demonstrated complementary detection of non-volatile and semi-volatile constituents across chromatographic and ionization modes.
• Multivariate statistics (PCA, HCA, PLS-DA, OPLS-DA) clearly separated oils by geographic origin and identified outlier Indonesian batches.
• Key markers such as β-vetivone (m/z 219.1760) distinguished origins, and ricinoleic acid (castor oil, m/z 298.2502) revealed adulteration undetectable by GC-MS.
• ASAP screening provided a rapid first-pass to flag contaminated samples in under five minutes.

Benefits and Practical Applications

• Comprehensive profiling extends quality control to non-volatile fractions of essential oils.
• Enhanced authentication workflow detects hidden adulterants and verifies botanical origin.
• Rapid HRMS-based screening accelerates batch release decisions.

Future Trends and Opportunities

• Integration of AI/ML algorithms for automated marker discovery and classification.
• Expansion of untargeted metabolomics to a wider range of natural products.
• Development of portable HRMS platforms for on-site quality control.

Conclusion

The combined UPLC/UPC²-HRMS metabolomics workflow coupled with advanced statistical tools offers a powerful approach for comprehensive profiling and authentication of vetiver essential oils. This method complements traditional GC-MS analyses by unveiling non-volatile adulterants and ensuring product integrity.

References

• Belhassen E., et al. Volatile constituents of vetiver: a review. Flavour Fragrance J. 2015;30:26–82.
• Marti G., et al. Comprehensive profiling in non-volatile citrus oil residues by MS and NMR. Food Chem. 2015;150:235–245.
• Mehl F., et al. Differentiation of lemon essential oil by volatile and non-volatile fractions: a metabolomic approach. Food Chem. 2014;143:325–335.
• Farag M., et al. Metabolomics analysis of artichoke leaf via UHPLC-qTOF-MS. Phytochemistry. 2013;95:177–187.
• Sidibé L., et al. Der Chemica Sinica. 2012;3(5):1276–1279.
• Chalchat J-L., et al. Journal of Essential Oil Bearing Plants. 2008;11(5):468–475.
• Filippi J-J. Flavour Fragrance J. 2014;29:137–142.
• Champagnat P., et al. J Essent Oil Res. 2006;18:647–649.
• Champagnat P., et al. OCL. 2006;2–3(13):190–194.
• Champagnat P., et al. Flavour Fragrance J. 2007;22:488–493.
• Kanaya S. et al. KNApSAcK database entry for Vetiveria; accessed 2019.