Gas Chromatography - Term Paper Example

It is also referred to as gas separator or aerograph. Gas chromatography is different from other forms of chromatography because the solutions are always in gas state as they travel through the column. Retention time occurs when different compounds separate in the column at different times. The gases have different eluting times due to the reactions between them and the column. The gases are now compared by their different retention times which give the gas chromatography the power to analyze the gases (Eli, pp. 217-220). Chromatography originated in 1903 by Mikhail Semenovich Tswett who was a Russian botanical scientist.

He opened the way to gas chromatography. He used adsorbents like ethanol and calcium carbonate to elute carotenoids and chlorophylls this saw the use of the column chromatography. The foundation of the gas chromatography was later laid by the Nobel Prize winner John Porter Martin. In 1941, he used the liquid to liquid method and in 1944, paper chromatography which brought about gas chromatography. It later led to the formation of liquid-gas chromatography in 1950. This has led to the modern gas chromatography technique which is being used today as an important analytical technique in chemistry (Colin, pp. 161-165). The description of chemistry, physics and biology behind the gas chromatography technique can be explained .

This means it uses the inert gases like carbon dioxide, helium, nitrogen and argon. For one to choose the carrier gas, he or she needs to identify the type of detector to be used. It has a molecular sieve that sieves out impurities and water (Casimir, pp. 139-142).The injector port is a column in which the samples are passed in the instrument. The samples are not supposed to be very large and they are to be introduced in the column as in the state of vapor. Large sample injections can cause the band to broaden thus lose resolution.

The most accurate and common method used is that of injecting samples via a rubber septum using the micro syringe. The injector is characterized by a heated chamber which has a glass liner where the sample is passed through the septum. When the injector is using the splitter mode, the carrier gas normally enters the chamber and leaves it by three outlets. Then the sample becomes vapor which leads to the formation of the mixture of carrier gas, vaporized solutes and solvents. A small amount of the mixture goes to the column leaving most of it to exit via the split outlets.

Components can not enter the column due to the septum purge outlet in the instrument (Sawhney, pp.211-215).The column is divided in to two sections; capillary and packed. The capillary is further divided in to two whereby there is the support or wall coated open tubular (WCOT, SCOT). The wall coated has a liquid coated stationary phase while the support coated one has thin layer of a supportive material that absorbs the stationary phase. The most efficient type of capillary is the wall-coated capillary.

The fused silica open tubular column is considered to be the best as it is a type of the WCOT.