Introduction
chromatography is a laboratory technique to separate two liquids. Of all the different types of separation methods, chromatography has the unique position of applying to all types of problems in all areas of science .it has undergone explosive growth in the last 30 years. the initial chromatographic experiments were independently carried out by David Day
the term chromatography and its principles were first discovered by Mikhail sweet .in his experiment, a leaf extract sample in patroleum ether was allowed to pass through the column of CaCo3 pure ether continued to flow through the column as a result of which various chlorophyll pigments etc. were separated into a series of the differently coloured and easily distinguished zone in the monograph he writes
If petroleum ether solution of chlorophyll is filtered through a column of absorbent, then pigments according to their adsorption sequence are resolved from to bottom into various colored zones. since the strongest adsorbed pigment displace the weaker adsorbed once and force them further downwards, .this separation become practically complete if after the pigment solution has flowed through one phase, a stream of pure solvent through the absorbent column like light rays in the spectrum, so the different component of the pigment mixture is resolved on the CaCo3 column according to law and can be estimated on it qualitatively and also quantitatively .such a preparation I term a chromatogram and the corresponding method chromatographic method
chromatography characterized by two important features:
- a huge interface area
- a dynamic way of operation which ensures more effective separation of substance as compared to other methods
chromatography can also be divided into the following general areas:
- adsorption chromatography
- partition chromatography
- exclusion chromatography
- ion-exchange chromatography
In adsorption chromatography, the stationary phase is solid(e.g., alumina-silica gel, etc.)the solute is adsorbed in different parts of the adsorbent column. The adsorbed component is then eluted by passing suitable solvent or eluted through the column .when column is used in such type of chromatography, the technique is known as column chromatography
in partition chromatography, the stationary phase may be liquid strongly adsorbed on a solid, which supports. In partition chromatography, the solute is distributed between the stationary liquid and the moving liquid (solvent) phases.
Exclusion chromatography is a process in which separation of the sample component occurs according to molecular size is called the exclusion chromatographic process. two newly developed exclusion chromatographic techniques are gel permeation and sieving separation
. Gel permeation has widely been used to separate sugar, polypeptide, protein, butyl rubber, polyethylene, polystyrene silicon, and many others
in sieving separation; nature and synthetic zeolites have widely been used. A typical zeolite called molecular sieve may be represented as AlO3,xSiO2,yH2O
ion-exchange chromatography is a type of liquid-solid chromatography in which separation is carried out in a column containing the resin, which acts as adsorbant
in ion-exchange chromatography, a reversible exchange of ions is effected between an ion in a liquid phase (mobile phase) and a solid, insoluble containing ionic sit(solid phase)
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