Gas Chromatography or Gas Liquid Chromatography is a technique Applied for separation, identification and quantification of components of a combination of organic compounds by selective partitioning between the stationary phase and mobile phase within a column followed by sequential elution of separated components. The technique is suitable for separation of substances having following characteristics:

• High volatility
• Thermal stability
• Low molecular weights
• Majorly, there are two gas chromatography forms into which it is classified — GLC or gas-liquid chromatography and GSC or gas-solid chromatography.

Both the methods utilize either solid or liquid as a stationary phase when using gas as the mobile phase. In Gas-solid chromatography, the retention of analytes is because of physical adsorption. On the other hand, gas-liquid chromatography separates the ions or molecules that are dissolved in a solvent. The underlying principle is — as the sample solution makes contact with the next liquid or solid phase, the solutes will begin interacting with the other stages. As a result of different adsorption rates, ion-exchanges, partitioning or dimensions, the interaction will change, and that is what is going to allow the separation of the mixed elements from one another. These differences will produce the sample mix pass at different rates throughout the column, as well as the chemicals can be separated.

 A Gas Chromatograph like any other analytical tool has evolved from one with several knobs and dials to one using a straightforward microprocessor-based keypad to control the operational parameters. · The simplification has caused simplicity of operation and time-saving. An understanding of the primary component parts will help in maximum use of system capacities. The gas chromatography includes a high peak capacity compared to other separation methods. Even though it has the power to separate an enormous number of compounds, there are a number of applications that need thousands of peaks to be split and we do not have sufficient theoretical plates to separate them via chromatography.  A frequent example of this is that the analysis of diesel that entails identifying trace analytes in complex matrices, such as food samples or environmental samples. The analysis can be carried out without complete chromatographic resolution through spectral resolution, where MS is hyphenated with GC. But this technique can be effective under the condition that the coeluting peaks have different spectra.