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Summary - unit 2 Practical procedure and techniques
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unit 2 Assignment 3 all the necessary information needed to complete this assignment is available in this document in order to achieve distinction.
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ChromatographyChromatography is defined as a technique used to separate solutes
based on the amounts present in a fluid stream that is moving. There
are two different types of phases in chromatography,
The mobile phase is a moving fluid phase. It may be either
liquid or gas.
The other phase is stationary, which can be either solid or
liquid.
A kinetic molecular motion is going inside the solute components,
allowing them to carry out the motion for migrating with the stream.
Chromatogram:
The chromatogram is produced by the separation in
chromatography. It is a paper chromatogram which is used for the
identification of pure and impure substances.
The pure substance produces only one stop on the
chromatogram paper.
The impure substance produces two or more spots on the
chromatogram paper.
A paper chromatogram is also used to relate two known substances.
For example, a chromatogram can relate and identify the substances
by their comparison with known substances. The two substances can
relate based on the two situations which are as follows,
They carry the same number and color as the spots.
Both substances have the same spots having the same Rf value.
, Rf value:
Rf stands for retardation or retention value, defined as the distance
of the analyte travelled on the solvent front of the chromatogram.
Rf = distance moved by the analyte
distance moved by solvent
The Rf values are the same for all the components in the same
solvent system. It varies from 0 which is not attracted to the solvent
system’s mobile phase, to 1 which is not attracted to the stationary
phase.
Paper chromatography:
Paper chromatography is a process in which a chromatogram paper
is used to distinguish the different rates of migration onto the
chromatogram paper. It is not much expensive process, but it is
much more useful and requires less material.
The method consists of adding a spot near the edge of the filter
paper which is being used to make a sample tested. The sample
is then placed into the solvent creating a liquid phase. As the
sample is soaked in the solvent, the spots start moving, relying
on their velocities, which depend on the solubility.
Afterwards, a point is noted when the spot has reached a
certain distance and then the distance is measured and the Rf
value is calculated.
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