Essential Oil Quality and Purity Evaluation via FT-IR Spectroscopy and Pattern Recognition Techniques

Abstract

Essential oils are highly volatile, aromatic concentrated extracts from plants with wide applications. In this study, fast, easy-to-use attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was combined with chemometric techniques to verify essential oils’ taxonomy and purity. Principal component analysis (PCA) clustered 30 essential oil samples into three different groups based on plant botanical family and concentration. The first group contained highly concentrated oils from the Asteraceae family, the second group contained highly concentrated oils from the Lamiaceae family, while the last group contained three highly concentrated essential oils from different botanical families and commercial-grade essential oils. Thus, commercial-grade oil samples did not cluster with the corresponding concentrated oil samples despite their similar spectral patterns or botanical family. A loading plot identified infrared (IR) bands that correspond to carbonyl, vinyl, methyl and methylene group vibrations as the most important spectral bands that can be used as marker bands for discrimination between different botanical plant family groups. Hierarchical cluster analysis (HCA) confirmed the results obtained by PCA. ATR-FTIR spectroscopy combined with chemometric algorithms provides a direct and non-destructive method for chemotaxonomic classification of medicinal and aromatic essential oils and an assessment of their purity.

Chemical Profile, Cytotoxic Activity and Oxidative Stress Reduction of Different Syringa vulgaris L. Extracts

“…Therefore, the peak occurring within range 1596–1608 cm −1 could be attributed to C=C stretching vibrations from the structure of both flavonols and iridoids [ 24 , 26 , 27 , 28 ]. Similarly, in the FT-IR spectra of S. vulgaris analyzed extracts, flavonols possess C–O–C, C=C and CH 3 functional groups which display peaks between 924–930 cm −1 , 1159–1162 cm −1 and 1385–1404 cm −1 respectively [ 20 , 23 , 27 , 28 , 29 ] ( Table 2 and Table 3 ).…”

“…Thus, peaks between 814–816 cm −1 , 1513–1515 cm −1 were characteristic to phenyl-propanoid-associated signals of echinacoside [ 21 , 22 ]. Within a similar range, terpene-associated stretching vibrations of C=O had contribution to band from 1694–1702 cm −1 [ 23 ]. Another terpene-associated peak was observed in the range 2901–2909 cm −1 and was caused by the C–H stretching vibration [ 20 , 23 , 24 , 25 ].…”

“…Within a similar range, terpene-associated stretching vibrations of C=O had contribution to band from 1694–1702 cm −1 [ 23 ]. Another terpene-associated peak was observed in the range 2901–2909 cm −1 and was caused by the C–H stretching vibration [ 20 , 23 , 24 , 25 ]. Furthermore, the peaks found between 885–890 cm −1 and 2925–2933 cm −1 were associated with the presence of CH 2 functional group, while the peak between 1256–1268 cm −1 could be attributed to C–O stretching vibration from both terpene and iridoids [ 23 ].…”

“…Another terpene-associated peak was observed in the range 2901–2909 cm −1 and was caused by the C–H stretching vibration [ 20 , 23 , 24 , 25 ]. Furthermore, the peaks found between 885–890 cm −1 and 2925–2933 cm −1 were associated with the presence of CH 2 functional group, while the peak between 1256–1268 cm −1 could be attributed to C–O stretching vibration from both terpene and iridoids [ 23 ]. A strong peak in the range 1076–1079 cm −1 was caused by iridoids stretching vibration of –C–OH [ 24 , 25 , 26 ].…”

Detection of Orange Essential Oil, Isopropyl Myristate, and Benzyl Alcohol in Lemon Essential Oil by FTIR Spectroscopy Combined with Chemometrics

“…Previous contributions proved the effectiveness of vibrational spectroscopy techniques such as FTIR and Raman spectroscopy for the determination of the authenticity of essential oils [ 15 , 17 , 42 , 43 , 44 ]. Additionally, previous applications of FTIR spectroscopy in combination with chemometrics shed light on the quality and purity evaluation of essential oils [ 45 ]. No previous study has investigated the adulteration of LEOs.…”