Isolation and Analysis of Essential Oils Using Gas Chromatography

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Isolation and Analysis of Essential Oils using Gas Chromatography

Lyndon Justin T. Guzman
Institute of Chemistry, University of the Philippines, Diliman, Quezon City Date Performed: February 2; February 4, 2011
Date Submitted: February 18, 2011


The purpose of this experiment is to isolate the essential oil from eucalyptus leaves as a pure compound; moreover, the components of the essential oil, camphor and limonene, will be then separated using gas chromatography technique, identify the components by their retention times, and compute for the concentration and percentage content of each component by their peak areas and peak heights. The volatile oil from eucalyptus leaves was isolated with the use of steam distillation setup, then using a separatory funnel to pipette out the extract from the distillate. A gas chromatography, with nitrogen gas as the carrier gas and a flame ionization detector, was used to separate and characterize the components of the essential oil. The retention times, peak areas, and peak heights were obtained for qualitative and quantitative analysis. A percentage of 0.05% and 2.85% were obtained as the content of camphor and limonene in the extracted oil, respectively. It also goes to show that limonene has greater concentration than that of camphor in the essential oil extract. Indeed, steam distillation and gas chromatography techniques are essential methods for extracting essential oils and separating natural compounds from plants.

I. Introduction

Gas chromatography is used for separations of volatile or reasonably volatile organic liquids and solids. In this method of chromatography, the components are partitioned between a liquid coating on the column (the stationary phase) and an inert gas (the mobile phase). The stationary phase for gas chromatography is usually an organic polymer coated on the inside of a tube, such as long capillary, and the mobile phase is an inert gas, such as hydrogen, helium, or nitrogen. (Druelinger, 2000)

Figure 1. Schematic diagram of a gas chromatographic system.

A small volume (1-10 μL) of a mixture of volatile substances (usually dissolved in a solvent) is injected by syringe onto a heated column through which an inert carrier gas is flowing. The heat applied, as well as the gas flow, helps the molecules from the sample travel through the column. Smaller, more volatile molecules generally emerge first from the opposite end of the column and are detected. The detector is connected to a recorder/data system, which shows a deflection when a sample passes the detector in proportion to the amount of sample detected. Compounds are eluted through an exit port either in an intact form or as combustion products, depending on the type of detector used. (Druelinger, 2000)

The characteristic aromas of plants are due to the volatile oils, or also known as essential oils, which have been used since antiquity as a source of fragrances and flavorings. These oils occur in all living parts of the plant; they are often concentrated in twigs, leaves, flowers, and seeds. Essential oils are generally complex mixtures of hydrocarbons, alcohols, and carbonyl compounds mostly belonging to the broad group of plant products known as terpenes. (Dalrymple and Moore, 1976)

One of the many types of samples easily characterized by the technique of gas chromatography is the essential oil. These essential oils are isolated from the plant tissue by steam distillation. Since organic compounds are generally miscible with one another, this phenomenon is usually observed only when one of the liquids is water with one or more immiscible organic liquids; in these cases, the distillation process is called steam distillation (Ault, 1983).

The technique of steam distillation is based upon the principle that each component of immiscible liquid mixtures contributes to the total vapor pressure as if the...
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