Raman spectroscopy as an analytical tool for analysis of vegetable and essential oils

摘要

Vegetable and essential oils are very important raw materials in the food, cosmetic and/or pharmaceutical industries. Vegetable oils are composed fundamentally of triglycerides (esters derived from glycerol and fatty acids). Triglycerides have different chemical characteristics depending on the seed or fruit from which they are extracted, with those containing unsaturated fatty acids being the most appreciated. Essential oils are composed of volatile compounds extracted from aromatic plants. Some of these volatile compounds are highly appreciated by the cosmetic and pharmaceutical industries. The economic relevance of vegetable and essential oils implies the need of appropriate analytical techniques to evaluate their quality. Raman spectroscopy is a remarkable non-destructive and versatile analytical technique that provides a fast identification of vegetable and essential oils. In this work, measurements were performed on 19 vegetable oils and 9 essential oils using a portable Raman spectrometer. The most important bands observed in the Raman spectra are discussed. It is difficult to distinguish vegetable oils from each other only by visual inspection of their spectra, because the spectra show important similarities. However, identification can be performed successfully using chemometric methods. On the other hand, essential oils can be distinguished by visual inspection, because their spectra show sharp characteristic bands. This work may serve as a basis for future works using Raman spectroscopy not only to confirm the authenticity of oils and the presence/absence of certain compounds in essential oils, but also to trace back their origin and the extraction methods used during the production process.