Quality Control Assays of Essential Oils Using Benchtop NMR Spectroscopy

The use of aromatic plants and their distilled oils by humans for medicinal or cosmetic applications dates back thousands of years.¹ While dozens of unique volatile organic compounds can typically be found in essential oils, their defining characteristics can be attributed to just a few molecules. For essential oil producers, these key molecules become analytes of interest during quality control (QC) assays, ensuring that the products are as expected, and that the components of interest are present within the expected concentration ranges.

The most common analytical techniques used for quantitative QC analyses within the essential oil industry remain gas chromatography (GC), high-performance liquid chromatography (HPLC), and mass spectrometry (MS). Due to the volatile nature of the components of interest in essential oils, GC is particularly common. Nuclear magnetic resonance (NMR) spectroscopy is often reserved for qualitative applications, as its powerful structural elucidation capabilities often make it the technique of choice when new compounds with unknown molecular structures are identified.^2,3

In our recent Magnetic Resonance in Chemistry publication, we demonstrated that benchtop NMR spectroscopy can be used to quantify key components in essential oils, such as terpenes, terpenoids, and aldehydes using an internal calibrant approach.⁴ The sample preparation described therein is facile, and the assays are performed within seconds or minutes. In the paper, we analyze essential oils of bergamot, lemongrass (Figure 1), lime, lemon, orange, mandarin, grapefruit, eucalyptus, and lavender. Taking advantage of the inherently quantitative nature of NMR spectroscopy, key analytes were all assayed using the same internal calibrant, since individual certified reference standards for each component of interest are not required.⁵ The quantified analytes include citral, linalyl acetate, linalool, decyl aldehyde, and eucalyptol.

Figure 1. ¹H (100 MHz) NMR spectrum of a lemongrass oil sample in DMSO-d₆/CDCl₃ (2:1).

For a full description of the methods and results, please read our full paper here. If you have any questions about the work included in this study, or if you are curious about how benchtop NMR technology could be added to your existing workflows, please don’t hesitate to contact us!

References 

(1)   Tisserand, R.; Young, R. Essential Oil Safety: A Guide for Health Care Professionals, 2nd ed.; Churchill Livingstone Elsevier: London, United Kingdom, 2014.
(2)   Dinkar Gore, D.; Ahmad, F.; Tikoo, K.; Kumar Bansal, A.; Kumar, D.; Pal Singh, I. Chin. Herb. Med. 2023, 15, 607–613.
(3)   Salvino, R. A.; Aroulanda, C.; De Filpo, G.; Celebre, G.; De Luca, G. Anal. Bioanal. Chem. 2022, 414, 2297–2313.
(4)   Araneda, J. F.; Leclerc, M. C.; Riegel, S. D. Magn. Reson. Chem. 2025. DOI: 10.1002/MRC.70049.
(5)   Pauli, G. F.; Chen, S. N.; Simmler, C.; Lankin, D. C.; Gödecke, T.; Jaki, B. U.; Friesen, J. B.; McAlpine, J. B.; Napolitano, J. G. J. Med. Chem. 2014, 57, 9220–9231.