Q.5. (a) Classify column chromatography techniques
Ans.5. (a) Column chromatography:Chromatography in which the substances to be separated are introduced onto the top of a column packed with an adsorbent (as silica gel or alumina), pass through the column at different rates that depend on the affinity of each substance for the adsorbent and for the solvent or solvent mixture, and are usually collected in solution as they pass from the column at different times.
Two types of column (or liquid) chromatography are generally used:
1. Adsorption chromatography:Adsorption chromatography is based on the interaction between the solute molecules and active sites on the stationary phase. This attachment or interaction depends on the polarity of solutes. This techniques proves the statement that “polar like polar”. Because if the stationary phase is more polar than the mobile phase then high polar compounds in the mixture will tightly bound to the stationary phase whereas less polar compounds will lightly bound to the stationary phase. Less tightly bound compounds will be eluted out by the mobile phase earlier than the tightly bonded ones.
2.Ion-exchange chromatography: Ion-exchange chromatography (or ion chromatography) is a process that allows the separation of ions and polar molecules based on their charge. It can be used for almost any kind of charged molecule including large proteins, small nucleotides and amino acids. The solution to be injected is usually called a sample, and the individually separated components are called analytes. It is often used in protein purification, water analysis, and quality control.
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