Descending chromatography
is a technique in which the mobile phase moves to 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.
Ascending chromatography is one of the chromatography technique used in which mobile phase run in upward direction opposite to the descending chromatography.
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.
Diagram:
 |
Types of Chromatography |
Procedure:
-To perform the Descending
chromatography Adsorption 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.
-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.
-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 components will 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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