Principle of Chromatography

• Chromatography is an analytical and preparative separation method in which substances are separated based on two phases i.e. stationary phase and mobile phase.
• The difference in migration rate is based on differential adsorption, partition, ion exchange, etc.

Techniques of paper chromatography

• The chromatography process takes place during the flow of solvent through the paper.

Steps:

• The start point is marked with a pencil at a suitable distance from the upper or lower end of the paper strip.
• The same solution is applied at the start point and the solvent is allowed to evaporate.
• Then, a chromatogram is put into the chromatographic tank which should be saturated with both the stationary and mobile phase.
• The paper is hung from a trough containing a mobile solvent system and the solvent flows downward by capillary.
• As soon as the solvent has traveled far enough, the chromatogram is taken out of the tank and allowed to dry.
• Detection is then carried out on the chromatogram.

α = Cs/Cm

where,

Cs = concentration at stationary phase

Cm = Concentration at mobile phase