Ascending Method in Paper Chromatography



ASCENDING METHOD

This is the simplest of all the
methods. The paper or strip is
suspended vertically into a closed jar
containing a suitable solvent)(mobile
phase). taking care that the dried spot
region remains above the solvent.The
solvent ascends through the fibres of
the paper by capillary action.The rate
of ascend is slow and decreases with
time because of gravity. In this
process, the components of the
mixture separate because of their
movement to different extents in the
direction of flow.When the solvent
has moved a suitable distance, the
paper is removed from the chamber.
The position of the solvent front is
marked with a lead pencil and the strip
is allowed to dry
If the substances are coloured, they
appear as separate spots. If the
substances are colourless, they need
to be sprayed with a locating reagent
for detection.
The development distance of a compound on the chromatogram is usually
expressed by Rf values( retention relative front ).

Rf = Distance of spot of component from the original line
_______________________________________

Distance of solvent from from the original line

Rf value does not exceed 1.00 and only two decimal places need to be
determined. The polarity of the component affects the Rf values. An increase in
the polarity lowers the Rf values and vice versa.

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