Raman spectroscopy in the detection of adulterated essential oils: The case of nonvolatile adulterants

Abstract

Essential oils are liquid mixtures of volatile compounds extracted from plants. Their quality is usually controlled via gas chromatography (GC), although with limitations when adulterants are nonvolatile substances. The essential oils of lavender (Lavandula angustifolia Mill.), peppermint (Mentha piperita L.), patchouli (Pogostemon cablin Benth), and their adulterated versions were measured by GC coupled to flame ionization detector (GC‐FID) and Raman spectroscopy. Canola oil, a nonvolatile substance, was used as the adulterant. The adulterated essential oils contained 1%, 3%, 5%, 10%, 15%, and 20% (v/v) of canola oil. Chromatograms of the adulterated essential oils containing 20% (v/v) of canola oil showed decrements in peak areas of the essential oil components, compared with peaks of the pure essential oils. The highest decrements were observed for the adulterated essential oil of patchouli. In general, detection of adulterated essential oils by simple visual inspection of the Raman features was difficult, due to slight differences observed in the spectra. Principal Components Analysis (PCA) allowed achieving a good spectral discrimination between pure and adulterated essential oils. These results suggest that Raman spectroscopy can overcome limitations of GC‐based methods, thus becoming an interesting alternative and complementary technique for quality control of essential oils.

Essential Oils and Their Individual Components in Cosmetic Products

“…It is worth mentioning that the simple determination of physico-chemical characteristics of the extracts may not be enough for evaluating some adulterations, and the use of more powerful analytical techniques may be required, e.g., gas and liquid chromatography, mass spectrometry, magnetic nuclear resonance, raman spectroscopy or infrared spectroscopy [83][84][85][86][87]. Figure 2 summarized the different steps for characterization of the purity of essential oils together with the advantages and disadvantages associated with the different analytical methodologies.…”

Adulteration identification of Hainan camellia (Camellia oleifera Abel.) oil based on comprehensive two‐dimensional gas chromatography and quadrupole time‐of‐flight mass coupled with chemometrics spectrometry

“…These results indicated that this method, when combined with PCA, can visually distinguish pure and adulterated camellia oils in the vast majority of cases. Adulteration in any percentage can be held liable, but low amounts of adulteration are intended only for bulk substances to increase the volume (or weight) of the product, and adulteration of less than 5% (v/v) is of a worthless nature (Vargas Jentzsch et al ., 2021).…”

Antibacterial and Antibiofilm Effects of Different Samples of Five Commercially Available Essential Oils

“…Due to increased demands and insufficient regulation, the adulteration of essential oils became a common practice along supply chains, generating safety concerns in the EOs industry [56]. The EOs adulteration could be performed using various methods: a cheaper oil addition [57] to the original one (e.g., corn mint to Peppermint oil), EOs' dilution with vegetable oils, and synthetic phytochemicals' inclusion [51] in the original EO [58][59][60]. Thus, supplementary quality control measures should be taken to ensure safety for human use [61,62].…”