Chromatography is a physical method of separation in which the components of a mixture to be separated are distributed between two phases – stationary and mobile. The stationary phase remains stationary, while the mobile phase moves in a definite direction.
This can be achieved by distributing the substance to be separated between two phases, a stationary, and a moving phase. Chromatography is considered as the most powerful and versatile technique of physical separation available to modern analysts. It was first used by Mikhail S. Tsvet, a Russian botanist to separate various plant pigments.
The analyte (sample of the mixture being analyzed) is applied and allowed to adhere to a stationary material known as the stationary phase or adsorbent. Another material, known as the mobile phase, carrier fluid, or eluent, is then made to flow through the adsorbent. During the process of chromatography, the analyte is separated into its components.
The basis of all forms of chromatography is the partition or distribution coefficient (Kd), which describes the way in which a compound distributes itself between two immiscible phases (say, solvents X and Y). The equation to represent partition coefficient is as shown below
Kd = Concentration of X / concentration of Y