Study of the Chemical Composition of Essential Oils by Gas Chromatography

ESTER R. CHAMORRO, SILVIA N. ZAMBÓN, WALTER G. MORALES, ALFREDO F. SEQUEIRA AND GUSTAVO A. VELASCO

Gas Chromatography in Plant Science, Wine Technology, Toxicology and Some Specific Applications

Intech

Lugar: Rijeka; Año: 2012; p. 307 - 324

The essential oils are complex mixtures, constituted by terpenoid hydrocarbons, oxygenated terpenes and sesquiterpenes. They come from the secondary metabolism of plants and are responsible for their characteristic aroma.   Their various applications arise a great interest in the study of oils.  Such applications may be found in the cosmetic industry, as ingredients of fragrances, decorative cosmetic, fine fragrances and flavouring, in the food industry, as aromas and flavours, in the pharmaceutical industry, as active components of medicines and as antibacterials/antimicrobials, and in aromatherapy.  At present, there are many studies where they are used as intermediary in reactions of fine chemistry, among other applications.   The methods used most for the industrial extraction of these oils are steam-distillation, extraction with solvents and expression.  Their selection will depend on the characteristics of the material from which the oil will be extracted, since they can be present in different parts of the plants, like the roots, the stem, the leaves, the fruits and/or the seeds.   Once the oils are obtained, the fundamental contribution of the organic chemical to the industry is its characterisation, as its chemical composition may vary even in one botanical species. These variations can be due to the presence of different chemotypes, according to its adaptation to the surrounding environment, as well as its state of development. We have to take into account the fact that it is the essential oils components what gives their intrinsic properties and economic value to them.   The development of the chromatography techniques has allowed us to make progress in the study of the chemical composition of the essential oils, being the gas chromatography (GC), in all ways, the best method, due to its simplicity, rapidity and efficiency,  in both the identification and measuring of its components and the study of its variations.   The aim of this chapter is to state the different applications of the gas chromatography (GC), from the quality control up to the identification and measuring of the chemical components of the essential oils of different aromatic species that grow in the northeast of Argentina, which have emerged as a result of years of experience in this topic.   As regards the applications of the gas chromatography (GC), different studies will be presented, among which the optimization of the operational conditions to separate the different components, the analysis of the variation of the composition of regional essential oils, the measuring, using internal standards, of oils as well as oils modified by fractional vacuum distillation, in addition to the study of the reactions of semi-synthesis reactions of high added value compounds, starting from oils or their components.