INTRODUCTION TO GAS CHROMATOGRAPHY

Gas chromatography is the process used to analyse the separation of compounds that can be vaporised without the decomposition process. There are various applications of gas chromatography, such as the: testing the purity of particular substances, separating different components of mixtures as well as determining their relative amount. Gas chromatography can also be used in the preparation of pure compounds from mixtures and identification of compounds in preparative chromatography. In chromatography, there are two phases namely; a mobile phase which includes a gas carrier such helium, hydrogen and nitrogen. Helium is the most unreactive and none flammable gas, also works with many detectors and older instruments hence most commonly used Anderson, (J. (Hoffman, P. G. , Lego, M. C. , & Galetto, W. In gas sample analysis packed columns are preferred although for most analytical separations capillary are most used for their efficiency and good peak separation and results (Soloshonok, V.

A. 2006) The capillary columns contain layers which are further divided into three parts, the parts make up its cross-section, and they include the following, polyimide coating, This is a protective coating applied to the outer surface of the column. Polyimide is mostly preferred because it gives the column a brown colour and make it more resistant to temperatures and it becomes flexible. Fused silica, the column should be made from an inert material, and it which with the compounds are separated, the most reliable material, therefore, is fused silica, its synthesis of quartz of high purity. These techniques may have a positive impact on sample turnaround. Tuneable selectivity is in its infancy and is showing significant reductions in analytical run times, with excellent control of peak resolution.

In a particular mode of operation, tuneable selectivity is termed stop-flow GC. Stop-flow GC utilizes conventional fused silica columns and a pulsed flow carrier gas operation. This technique is one of the latest discoveries in high-speed GC and significantly reduces analysis time. , & Perry, S. G. DETECTION METHODS USED IN GAS CHROMATOGRAPHY The most commonly used detectors are the flame ionization detectors and the thermal contactor detector. The two method of detections have common similarity among them: both are sensitive to the wide range of components and both works under the wide range of concentration are sensitive to a wide range of components, and both work over a wide range of concentrations. While the thermal contactor detector is universal and can be used to detect any component other than gas flame ionizing detector are sensitive to hydrocarbons that the thermal, however, they cannot detect water (Ahmadi, F.