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Different kinds of paper chromatography


Types of paper chromatography:



With the passage of time many types of paper chromatography have been developed based on the nature of mobile phase.
First type is ascending paper chromatography which is discussed as follows:
Ascending Paper Chromatography:


Defination of  Ascending paper chromatography:


Ascending paper chromatography can be defined as follows:
“In ascending paper chromatography the chromatogram is close contact in such  a way that the spot is Stirred with the solvent where the solvent is present  at theground.The developmental process for a chromatogram or spotting process for separation purpose is done against the force of gravity .Sothis technique is named as ascending paper chromatography”.
The name of this technique indicates that in this solvent travels in upward direction.
Experimental procedure of ascending paper chromatography:
Minimum amount of the mobile phase is introduced inside the developing chamber. Sample solution and reference solution are splashed at that line which is marked at  the ground of the paper,this paer is hanging at the top of the developing chamber with the help of hook or any other holding medium.

Another step is that, the suspended paper can be changed into the shape of the cylinder and kept in the developing chamber. Solvent travels to the top by the help of capillary action. As the rate of solvent front decreases with the passage of time then few remanants of the separated  components can be seen after the procedure of effective separation.
Important point for the developing chamber: 
It is important to note that  developing chamber should be covered with a lid for the maintainance of satirated atmosphere which is made with a saturated solvent inside the developing chamber. This saturation of atmosphere with the help of  vapours of a solvent to avoid the evaporation of that solvent which travels in upward direction.

Descending Paper Chromatography method:



Defination of Descending Paper Chromatographic  method:





“In this method the solvent front moves in downward direction along the length of paper which is hanging inside the developing chamber with the help of any hanging source” .On the upper surface of the chamber there is a tray  in which mobile phase is present. The paper with spot on the line marked at a distance of few centimeters from the top is clamped to the top. Preceding to elution the tank is covered with a plate  and calibrated with the vapors of the mobile phase.
The solvent moves  in a downward direction  with the help of two actions capillary action and the pull of the gravity.


Advantage of Descending Paper Chromatography method:



The advantage of this dramatic method the process of  development can be repeated again and again without letting up even even if the solvent moves towards the bottom end of the paper.

Ascending and Descending Chromatography:

In this latest version the solvent first moves in upward direction of the paper which can be wrapped  over a rod and it continues to travel in downward direction  after crossing the rod.
Benefit of this technique:
This array permit longer development period for better  separation of complex mixtures

Two-Dimensional Chromatography:

Two dimensional chromatography helps us to identify and separate those substances which have same Rf value. Only small amount of mixture is introduced near to one corner of  the standard on the filter paper which is in square shape. After this the paper is kept for the process  of development either by  ascending or descending mode and at the end paper is allowed to dry.
Rotation of filter paper:
The clear out paper is now circled ninety° so that the edge having the collection of separated spots is at the bottom and allowed to broaden in the equal or a exclusive solvent segment
the association helps to remedy the spots in two-dimensions by means of spreading the spots on the filter out paper.
Horizontal or Circular Paper Chromatography:
Horizontal or circular paper chromatography lets in separation of sample components within the shape of concentric circular zones thru radial motion of liquid section. A circular formed filter out paper is employed and one of a kind arrangements are used. A slim slit about 2mm extensive is reduce from the circumference to the centre and the wick shaped is bent so one can dip in the solvent contained in a petri dish. Sample spotting is accomplished along the circumference of the smaller inner circle. The petri dish is covered after securing the filter out paper to the top and allowed to increase. The cell segment reaches the clear out paper through capillary motion and spreads radially outwards thereby resolving the pattern additives radially. In this association there may be no want to reduce a wick. A small capillary is inserted through an adjustable collar positioned inside the solvent within the petri dish. After applying the pattern spot to the centre of a circular filter out paper it's miles protected with a petri dish cover and allowed to expand. As before the solvent is drawn up with the aid of capillary movement of the filter paper and spreads radially outwards thereby resolving the sample elements radially.

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