Adsorption Chromatography Assignment.pdf

Adsorption Chromatography.

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ADSORPTION CHROMATOGRAPHY
Topic Outlines:
✓ Absorption versus Adsorption.
✓ Introduction of Adsorption Chromatography.
✓ Conditions.
✓ Principle of Adsorption Chromatography.
✓ Diagram & Procedure of Adsorption Chromatography.
✓ Experiment (TLC).
✓ Types of Adsorption Chromatography.
✓ Applications of Adsorption Chromatography.
✓ Advantages & Disadvantages of Adsorption Chromatography.

Absorption Versus Adsorption:
These are two different terms:
→ In absorption, one substance penetrates into the bulk of another substance.
→ Adsorption is a surface phenomenon where interaction takes place only on the
surface of one substance.
Introduction of Adsorption Chromatography:
A Russian botanist, Mikhail Tsvet in the year 1901, invented the process called
adsorption chromatography while doing his research on plant pigments.
Adsorption Chromatography:

Adsorption chromatography is the oldest types of chromatography technique. It makes
use of a mobile phase which is either in liquid or gaseous form. The mobile phase is
adsorbed onto the surface of a stationary solid phase. It can be defined as;
“As a technique for the separation of the component in a mixture by adsorption
from a mobile phase into the stationary solid surface.”
Conditions:
Adsorption chromatography depends on the following condition:
❖ The selection of the adsorbent
❖ The choice of the solvent for the sample mixture
❖ The rate of flow of the solvent
❖ The temperature
❖ The selection of the column size
Principle of Adsorption Chromatography:
• Adsorption Chromatography is based on the principle that some solid substances,
which are known as adsorbent, have the power to hold molecules at their surface.
• This holding force is due to weak, non-ionic attractive forces of the van der Waals'
and hydrogen bonding, which only occur at specific adsorption beds.
• As solvent (eluent) is constantly passed over the adsorbent (stationary phase) in
the column. The most commonly used adsorbents are silica, alumina, and carbon.

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Adsorption Chromatography Diagram:

Adsorption Chromatography Procedure:
Before beginning an adsorption chromatography experiment, we must recognize the
various components essential to perform the process.
o Stationary phase: The stationary phase of adsorption chromatography is
adsorbent.
o Mobile phase: In adsorption chromatography, either a liquid or a gas is used as a
mobile phase.
Apparatus:
▪ Chromatography jar: The glass jar has a lid. It helps to maintain a proper
environment during separation.
▪ Thin-layer chromatography plate: Silicate glass plate with size 20*20 cm,
20*5 cm, 20*10.
▪ Capillary tube: Sample mixture is applied to TLC with the help of this tube.
▪ Mobile phase: Liquid or gas.
▪ Stationary phase: Adsorbents.

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Experiment (TLC):
o Take a clean and dry chromatographic jar.
o To make sure that the environment in the jar is saturated with solvent vapors, a
paper soaked in the mobile phase is applied to the walls.
o Add the mobile phase to the jar and close it and maintain equilibrium
o Mark the baseline on the adsorbent.
o Apply sample to TLC plate with the help of a capillary tube and allow it to dry.
Put the plates in the jar and close it.
o Wait until the solvent moves from the baseline.
o Take out the TLC plate and dry it.
Types of Adsorption Chromatography:
These are some important types of Adsorption Chromatography.
1. Thin Layer Chromatography (TLC).
2. Paper Chromatography.
3. Column Chromatography.
4. Gas-Solid Chromatography.
1- Thin Layer Chromatography (TLC):
 It is an analytical method of separation used for qualitative analysis and
monitoring of the reaction as well as identifying unknown compounds.
 In which the mobile phase moves over an adsorbent.
2- Paper Chromatography:
 It is a technique that uses paper sheets or strips as the adsorbent being the
stationary phase through which a solution is made to pass is called paper
chromatography.
 The solid surface of the paper is the stationary phase and the liquid phase is the
mobile phase.
3- Column Chromatography:
 It is a commonly used technique for separating the compounds from the sample
mixture. It is used on small or large scans to separate and purify compounds.
 The mixture of samples moves through the stationary phase with the mobile
phase and based on various degrees of adhesion it separates the compounds.
4- Gas-Solid Chromatography:
 It is an analytical method for the separation of volatile compounds in which the
mobile phase is gas and the stationary phase is suitable for solid support.
 The gas-solid chromatography, work on the principle of separation is adsorption
and generally used for samples that had less solubility in the stationary phase.
Adsorption Chromatography Applications:
Adsorption chromatography have the various applications:
• It is used for the separation of amino acids.
• It is used in the isolation of antibiotics.

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• It is used in the identification of carbohydrates.
• It is used to determine the concentration of a molecule.
• It is used for the separation and identification of isomers.
• Used to isolate and determine various peptides and proteins.
Advantages of adsorption chromatography:
The advantages of adsorption chromatography are as follows.
▪ Adsorption chromatography is an important tool for separating many molecules
that cannot be distinguished from other methods.
▪ Adsorption chromatography uses a broad range of mobile phases.
▪ The molecules in the complex mixture can be easily separated.
▪ Very few types of equipment are used as opposed to other separation methods.
Disadvantages of adsorption chromatography:
The disadvantages of adsorption chromatography are as follows.
▪ Automation is making it more complicated and expensive.
▪ The major disadvantage of adsorption chromatography is that some solutes have
longer retention times.
▪ It can cause catalytic variations in the sample.
▪ Results obtained by some methods of adsorption chromatography are difficult to
reproduce.








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