chromatography, types, paper chromatography, ascending, descending, working principle, applications

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DESCENDING PAPER
CHROMATOGRAPHY
By;
P.Rajeshwari
I, M.Sc Biotechnology

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DEFINITION:
▪ Descending chromatography is a techniquein which the mobile phase
movesto the downside.
▪ Paper chromatography and thin-layer chromatography is the technique in
which Descending chromatography is used.
▪ Ascending chromatography is one of the chromatography technique used
in which mobile phase run in upward direction opposite to the
descending chromatography

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PRINCIPLE:
▪ In descending chromatography, the mobile phase runs to the downside
because of the gravitational force.
▪ It works on the principle of adsorption chromatography and the partition
chromatography.
▪ The term descending is given because the separation or the development
of the chromatogram is taking place towards down.

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DIAGRAM:

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PROCEDURE:
▪ To perform the Descending chromatographyAdsorption filter paper/TLC
plate, solvent as mobile phase, glass chamber with lid or beaker with
lead, fine capillary for spotting is required.
▪ Descending chromatography set up is opposite to the ascending
chromatography. The mobile phase tank is set at the top of the assembly.
It is a quite complex setup than the Ascending chromatography.

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▪ The mobile phase tank is placed at the top side of the assembly as shown in
the diagram. The chamber needs to be saturated before the separation takes
place.
▪ The spotting procedure in descending chromatography is the same as the
Ascending chromatography. Syringe or glass capillary spotting of the mixture
of the analyte is a place on the stationary phase at the marked place.
▪ After the spotting of the analyte, adsorption paper or the thin layer plate is
attached at the top side in the chamber.

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▪ The mobile phase gradually moves from the upper side to the downside.
Along with the mobile phase spot of the analyte also moves with the
mobile phase and its componentswill separate out
▪ The spot with a mixture of analyte travel through the mobile phase and
separation of the analyte is observed on the paper in the form of the spot
after drying.
▪ Reagent in case visual inspection of the spot is not possible (To visualize
the spot).

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APPLICATION OF PAPER
CHROMATOGRAPHY:
▪ To study the process of fermentation and ripening.
▪ To check the purity of pharmaceuticals.
▪ To inspect cosmetics.
▪ To detect the adulterants.
▪ To detect the contaminants in drinks and foods.
▪ To examine the reaction mixturesin biochemical laboratories.
▪ To determinedopes and drugs in humansand animals.