Principles and Practice of Chromatography - Chromatography Applications > Gas Chromatography Applications > Essential Oils > Page 76

Essential Oils

Without the use of gas chromatography the analysis of essential oils would be extremely difficult. Prior to the technique being developed, only the major components of the oils could be separated, achieved by distillation with high efficiency columns. Even so, such columns rarely contained more than 100 theoretical plates (distillation plates), were very slow in operation, and took many days to complete an analysis. Due to the limited separation efficiency of the distillation column, even the major components were contaminated with traces of materials, many of which had strong olfactory intensity and thus confused the olfactory character of the major component. The gas chromatograph had a startling impact on the essential oil industry. Not only was the complex nature of the raw materials disclosed for the first time, but the character of each pure individual components could be accurately ascertained by olfactory assessment of the eluted peaks (using a non destructive detector such as the katherometer, and smelling them).

The first separations of essential oils were carried out on packed columns that provided limited efficiency but, nevertheless represented a tremendous advance on distillation. The introduction of the technique of temperature programming improved the separation even more. However, it was not until the capillary column, with its many thousands of theoretical plates, became commercially available that the true complex nature of many of the essential oils was revealed. The chemical structure of the individual components of many of the oils, elucidated by the GC/MS tandem systems, provided the knowledge necessary to synthesize a number of commercially important synthetic flavors. For example, the synthetic flavors that closely imitate those of the peach, melon and other fruits that are presently available to the contemporary food chemist are a direct result of the separating capabilities of gas chromatography.