CHROMATOGRAPHY
Chromatography (from Greek word Chroma means “color” and Graphein means “to write”) is the collective term used for the separation of the mixture. The mixture is dissolved in a fluid called the mobile phase, which carries it to another material known as the stationary phase. The separation is based on the speed of different constituents of the mixture and on the differential partition of the mobile and the stationary phase (web link7).
Distribution or partition coefficient is the basis of chromatography which describes a way in which constituents of a mixture distributes between two immiscible phases. For two such phases A and B, the value for this coefficient is a constant at a given temperature and is given by the expression (36): Kd = Concentration in phase A Concentration in phase B

COLUMN CHROMATOGRAPHY
For separations of solid and liquids, column chromatography is one of the most important techniques. It is a solid liquid separation technique in which the stationary phase is solid and the mobile phase is liquid. It is based on the principle of differential adsorption of the substance by adsorbent (web link 8). The stationary phase is packed into a glass or metal column and mixture of analytes are then applied, the mobile phase (eluent) is passed through the column either by use of a pumping system or applied gas pressure. The stationary phase is either coated onto discrete small particles (the matrix) and packed into the column or applied as a thin film to the inside wall of the column. As the eluent flows through the column the analytes separate on the basis of their distribution coefficients and emerge individually in the eluate as it leaves the column
ADSORBENT
Adsorbents usually used in column chromatography are silica gel, alumina, calcium carbonate, calcium phosphate, magnesia,