Chromatography is a technique used to separate and identify the components of a mixture. It works by allowing the molecules present in the mixture to distribute themselves between a stationary and a mobile medium. Major objective of this lecture is to present on Gas Liquid Chromatography. In gas-liquid chromatography, the mobile phase is a gas such as helium and the stationary phase is a high boiling point liquid adsorbed onto a solid. Here also briefly present on chromatogram of petrol and thin layer chromatography.