Chromatography : It is a type of separation process in which the liquid or gas is separated into components at different rate.
It involves passing the mixture through a stationary phase, which separates the analyte to be measured from other molecules.This is possible because the components which get adsorbed to the stationary phase moves slowly with the mobile phase whereas the components which do not get adsorbed to the stationary phase move faster with the mobile phase.
Hence, chromatography is a laboratory technique that is used to separate mixtures according to the rates their components travel through a material
The hint you should note here is the 'travel through a material'. From this, you can think of separation techniques where the components have to go through a material. This could be filtration or membrane separation. However, in filtration, the rate is not a factor. You only have to separate solid from liquid. For membrane separation, you can separate two liquids based on their permeability to the membrane.
Because: The mixtures contain unwanted substances which may be harmful and may degrade the properties of mixtures. So we, need to separated them and extract useful substances.
