Write about thin layer chromatography $(TLC)$.

(N/A) Thin layer chromatography $(TLC)$ is a type of adsorption chromatography in which the separation of the components of a mixture is achieved over a thin layer of an adsorbent.
$TLC$ Plate: $A$ thin layer (about $0.2 \ mm$ thick) of an adsorbent (such as silica gel or alumina) is spread over a glass plate of suitable size. This plate is known as a thin layer chromatography plate or chromaplate.
Procedure:
$(i)$ The solution of the mixture to be separated is applied as a small spot about $2 \ cm$ above one end of the $TLC$ plate.
$(ii)$ The glass plate is then placed in a closed jar containing the eluant (solvent).
Observation: As the eluant rises up the plate,the components of the mixture move up along with the eluant to different distances depending on their degree of adsorption,and separation takes place. The relative adsorption of each component of the mixture is expressed in terms of its retardation factor,i.e.,$R_{f}$ value.
$R_{f} = \frac{\text{Distance moved by the substance from base line}}{\text{Distance moved by the solvent from base line}} = \frac{x}{y}$
Where:
$x = \text{Distance moved by the substance from base line}$
$y = \text{Distance moved by the solvent from base line}$
Note: The $R_{f}$ value of every component is specific and different for different components in a mixture.