A Novel qNMR Application for the Quantification of Vegetable Oils Used as Adulterants in Essential Oils

Abstract

Essential oils (EOs) are more and more frequently adulterated due to their wide usage and large profit, for this reason accurate and precise authentication techniques are essential. This work aims at the application of qNMR as a versatile tool for the quantification of vegetable oils potentially usable as adulterants or diluents in EOs. This approach is based on the quantification of both 1H and 13C glycerol backbone signals, which are actually present in each vegetable oil containing triglycerides. For the validation, binary mixtures of rosemary EO and corn oil (0.8–50%) were prepared. To verify the general feasibility of this technique, other different mixtures including lavender, citronella, orange and peanut, almond, sunflower, and soy seed oils were analyzed. The results showed that the efficacy of this approach does not depend on the specific combination of EO and vegetable oil, ensuring its versatility. The method was able to determine the adulterant, with a mean accuracy of 91.81 and 89.77% for calculations made on 1H and 13C spectra, respectively. The high precision and accuracy here observed, make 1H-qNMR competitive with other well-established techniques. Considering the current importance of quality control of EOs to avoid fraudulent practices, this work can be considered pioneering and promising.

Multivariate Statistical Models for the Authentication of Traditional Balsamic Vinegar of Modena and Balsamic Vinegar of Modena on 1H-NMR Data: Comparison of Targeted and Untargeted Approaches

“…Acquisition parameters for “zgcppr” were as follows: time domain (number of data points), 64 K; dummy scans, 2; acquisition time, 3.90 s; delay time, 5 s; pulse width, 12 μs; number of scans, 64; spectral width, 14 ppm (8403.4 Hz); fid resolution, 0.1282 Hz; digitalization mode, baseopt. The total acquisition time was 6 min and 49 s. Since the use of the correct delay time (D1) is fundamental to assure the accurate quantification of considered compounds, the exact T1 for all the analytes and pyridoxine protons were measured using the Bruker Sequence “T1IR”, and the acquisition parameters were as follows: a list of 10 increasing delay times (from 10 ms to 30 s); delay time, 30 s; number of scans, 1; total acquisition time, 6 min and 54 s. A D1 time equal to five times the biggest T1 was used [ 27 ].…”

“…The Mnova tool requires a multiplet analysis for the integration. Therefore, after the initial spectra processing, a manual multiplet analysis was carried out, and the peak area of signals belonging to the target compounds was compared to the area of signals generated by the pyridoxine standard solution (external reference) [ 27 ]. The pyridoxine solution in DMSO- d 6 (4.98 mM) was prepared immediately before the acquisition and analyzed under the same experimental parameters.…”

Quality Standards and Pharmacological Interventions of Natural Oils: Current Scenario and Future Perspectives

“…In fact, the adulteration of these priceless items has become more common because of the rising demand for cheaper EOs from other natural sources or from vegetable oils, with higher profits as the main motivation. 39 Because of its excellent characteristic features, lemon oil is utilized as a component in body care products, cosmetics, and pharmaceuticals. Lemon essential oil is a high-value natural product that is very significant economically all over the world.…”

An Optimized Two-Dimensional Quantitative Nuclear Magnetic Resonance Strategy for the Rapid Quantitation of Diester-Type C19-Diterpenoid Alkaloids from Aconitum carmichaelii

“…Quantitative nuclear magnetic resonance (qNMR) is a general term for quantifying 1 H, 13 C, 14 N, 19 F, or 31 P nuclear magnetic resonance signals of target compounds or components using 1D NMR (e.g., 1 H, 13 C, 14 N, and 19 F NMR) spectra − or 2D NMR (e.g., 1 H- 1 H COSY, 1 H- 13 C HSQC, and 1 H- 14 N HSQC) spectra. − Since qNMR was first reported in 1963, it has shown incomparable application potential in natural products, metabolites, and pharmaceutical analysis . Quantitative 1 H NMR has been recognized as a general quantitative method, which has been widely used in purity determination, , content determination, metabolic analysis, , authenticity identification, , quality control, , and other applications due to its advantages of nondestructive analysis, short measuring time, and simple methodology, and because it does not require a specific reference standard . However, the inherent problem of a narrow spectral width of 1 H NMR has attracted increasing attention from researchers, as this issue can lead to poor signal resolution , and complicated data processing procedures …”