Chromatography

CHROMATOGRAPHY

The term Chromatography is a relatively new separation technique. In Greek, the term 'Khromatos' means ‘color’ and term 'graphos' means ‘writing’.

The Chromatography-technique was first discovered by Russian biologist Dr. Micheal Tswett in 1906, for the separation of color plant pigment on a column of alumina.

Nowadays various types of Chromatography are in use to separate almost any given mixture whether color or colorless into it’s as an analytical technique employed for the inorganic substance. Separation method is used for qualitative identification and quantitative determination.

Chromatography is a name given to technique by which members of a group of similar substance are separated by continuous redistribution between two phases. The first one is stationary phase and second is mobile phase.

Introduction Principle, Types & Uses

1.      Paper Chromatography

2.      Thin Layer Chromatography

3.      Column Chromatography

4.      Lon Exchange Chromatography

5.      Affinity Chromatography

6.      Gel Chromatography

Chromatographic Method	Basis
Adsorption Column Chromatography	Distribution of solute between solid and liquid phase on a column
Partition Column Chromatography	Distribution of solute between two liquids on a column
Paper Chromatography	Partition on a sheet of paper
Thin Layer Chromatography	Adsorption of partition on thin sheets
Ion Exchange Chromatography	Exchange of ion
Gel Permeation Chromatography	Size of solute
Gas Chromatography	Distribution of gaseous solutes between a gas, liquid/solid phase.
Electrophoretic  Chromatography	Separation on a sheet in the presence of an electric field

Chromatography – 2 classes

The two classes of Chromatography are,

1.      Gas

2.      Liquid Chromatography

a.      Adsorption

b.      Partition

c.       Ion Exchange

d.      Electrophoretic

Chromatography technique separates molecule on the basis of difference of size, shape, mass, charge, solubility, and adsorption properties. There are many different types of chromatography but they all involve interaction between three components.

a.      Mixture to be separated

b.      Stationary phase (solid phase which supports)

c.       Solvent system (mobile phase which moves over the stationary phase)

Basis of separation

            In chromatography, two immiscible phases (i.e. stationary and mobile phases) are brought into contact with each other. The mobile phase undergoes a series of interaction between stationary and mobile phases as it is being carried through the system by mobile phases. The difference in interaction governs the rate of migration of individual components under the influence of mobile phase. Under suitable condition, the resulting different rates of migration can bring about complete separation of the substance.

Solute property used for Chromatography separation

Technique                                                                  Solute Property

1. Adsorption                                                       a. Adsorption of particle
2. Partition                                                          b. Solubility
3. Ion exchange                                                   c. Ionization
4. Gel                                                                   d. Size and shape

Based on nature of stationary phase and mobile phase

                                                                                          Stationary      Mobile

1. Adsorption Chromatography                                      Solid                Liquid/gas
2. Partition Chromatography                                          Liquid              Liquid/gas
3. Gas Chromatography                                                  Solid/Liquid     Mixture of gas

Adsorption Chromatography

The technique in which stationary phase is solid and mobile phase is liquid/gas is adsorption Chromatography. The solid are absorbed in different parts of adsorbent column. Then adsorbent component are eluted by passing suitable solvent through column.

Partition Chromatography

The technique in which stationary phase is liquid, frequently water and mobile phase can be either liquid/gas.

Gas Chromatography

The stationary phase is solid/liquid and mobile phase is mixture of gas, inert gas, nitrogen, helium, argon.

Two types of GC are:

1. Gas – Solid Chromatography (Stationary Phase is Solid)
2. Gas – Liquid Chromatography (Stationary Phase is liquid)

Modes of Chromatography

Chromatographic separation may be achieved by using three modes

1. Column Chromatography
2. Thin layer Chromatography
3. Paper Chromatography

Column Chromatography

Column Chromatography is which stationary phase is attached to a suitable matrix is packed into a glass or metal column and the mobile phase is passed through the column either by gravity feed or by the use of pumping system or applied gas pressure. It is the most commonly used mode of Chromatography.

Thin Layer Chromatography

Thin Layer Chromatography in which the stationary phase attached to a suitable matrix which is coated thinly on to a glass or plastic plate. The mobile liquid phase passes across thin layer either horizontally or vertically.

Paper Chromatography

In Paper Chromatography, stationary liquid phase is supported by cellulose fiber of a paper sheet and the mobile phase passes along the gravity feed or capillary action over the stationary phase incorporated into a solid supporting material, cellulose.