Adsorption chromatography

It is a type of chromatography. Used in the seperation of compound. Comes under the instrumentation

1. ADSORPTION CHROMATOGRAPHY Prepared by, R Sharmila

2. INTRODUCTION: Developed by American scientist, D. T. Day. Later M. S. Tswett , botanist used adsorption columns, for the investigation of plant pigments.

3. PRINCIPLE: In this chromatography, seperation of components of a mixture takes place by the adsorption efficiency of the sample. The most strongly adsorbed component forms the topmost band. the least adsorbed component forms the lowermost band on the adsorbent column. Degree of separation depends upon the separation of surface area of adsorbent.

4. The distribution co-efficient is given by Amount of solute per unit of stationary phase K = ------------------------------------- Amount of solute per unit of mobile phase

5. TYPES OF ADSORBENTS: There are number of adsorbents commercially used. The most commonly used adsorbents in adsorption chromatography are Fullers earth Powdered charcoal Polystyrene beads Silica gel Alumina oxide

6. FULLERS EARTH: It consists of a mixture of minerals obtained from certain clay deposits. It is widely used to decolorize the food. Used in the removal of pigments from wine sample. It is cheap. It sold under the name of Florisil .

7. POWDERED CHARCOAL: Powerful adsorbent Resource material are bone, coconut Finely divided charcoal is very difficult to wet Preparing a column packed with charcoal is very troublesome

8. POLYSTYRENE BEADS: It is modified as tiny beads It doesnot have any charged groups in its surface. Function is only adsorption Useful in the separation of alkaloids, steroids Commercial name is XAD resins

9. SILICA GEL: It is a popular adsorbent It is less stable than alumina It should handled properly to avoid changes in the result It is available in the form of crushed and powdered glass

10. ALUMINA: It is powerful adsorbent It is prepared as a precipitate of aluminium hydroxide

11. PREPARATION OF THE COLUMN : DRY PACKING The powdered sample is poured inside the tube (both the sample and the stationary column remain dry) WET PACKING The bottom of the tube is closed The column is filled with solvent This method is known as wet packing

12. APPLICATIONS Used for the separation of Polycyclic aromatic compounds Plasma cortisol Geometrical isomers