Gas chromatography is an analytical chemical method for separating chemical substances.

The sample (here: fragrances) is carried by a moving gas stream through a tube packed with a finely divided solid. Because of their chemical characteristics, the substances are held back differently by the material in the tube so that they leave the apparatus one after the other.

A detector at the end of the tube is used for distinguishing of the individual substances. The detector, normally another analytical tool, is in our case replaced by an extremely sensitive human detector - the nose!

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   Description of the Experiment   

3 different flavour components are separated in the gas chromatograph. Initially the visitor is given a mixture of three fragrance components to sniff. (The visitor is not able to identify the components when offered as a mixture!) The components used are benzaldehyde (from bitter almond oil), eucalyptole (from eucalyptous oil) and eugenole (from clove oil).

The mixture is then injected into the GC-system. The visitor starts the experiment with the touch screen. While the GC system is working, animations are shown on the touch screen explaining what is going on inside. The visitor can smell the separated fragrance components when they leave the GC and guess which flavour compound it was.
In a kind of Quiz the visitor is asked to decide what (s)he is smelling. The visitor can indicate his/her decision by touching one of four bottles on the touch screen named "bitter almond", "eucalyptus", "rose" (a dummy) and "clove" and move it on to the peak of the chromatogramme formed on the screen. This assignment is repeated for each fragrance. When the experiment is finished the visitor can exchange the perfume bottles and correct the choice if (s)he maybe thinks that the decision was wrong. Then visitor gets the information if the assignments were correct or not.

During the experiment the visitor can also watch a short film about the production of "rose oil".
The 'smelling microphones' on the left side of the experiment can be used to practise the nose. The pure fragrances leave the 'microphone' by pushing the button. 'Microphones' are used for design reasons only.

   Duration   

The whole experiment lasts about 6 minutes.

   Conclusion   

Gas Chromatography is one of the most important tools in chemistry because of its simplicity, sensitivity and effectiveness in separating components of mixtures. It is widely used for quantitative and qualitative analysis of mixtures and for the purification of compounds.

   Detailed Conclusion   

Gas Chromatography can be defined as differential migration processes where gases or vaporised sample components are selectively retained by a stationary phase.

Chromatography in general has another main branch: Liquid chromatography. It is a widely used separation technique using also sample partition between two phases: a stationary phase of large surface area and a mobile liquid which percolates over the stationary bed. In contrast to Gas Chromatography, traditional Liquid Chromatography is a rather slow technique taking hours and days to run a sample. To overcome the disadvantages of traditional Liquid Chromatography, High Pressure Liquid Chromatography (HPLC) has been developed.
It offers several advantages as high speed, high resolution and high sensitivity.

Modern chemistry without Gas Chromatography, Liquid Chromatography and HPLC is unthinkable!