BTEC Applied Science Unit 2 Assignment C

Chromatographic Techniques
TLC AND PAPER CHROMATOGRAPHY OF EXTRACTED
PLANT PIGMENTS

Aims
Undertake chromatographic techniques to identify components in mixtures




Introduction
Chromatography is a separation method used in laboratories to separate compounds inside a
sample. A stationary phase and a mobile phase are used in chromatography to create a
chromatograph.

- In paper chromatography, the stationary phase is the solid that the mobile phase moves up
in thin layer chromatography, this is typically cellulose paper.
- The solvent in the mobile phase flows in one direction, capillary action moving the substance
along the stationary phase.
- The end product is a chromatograph, which is the result of the components moving up the
stationary phase. This will display the components and from there, the Rf value can be
calculated.



The retention factor- known as the Rf value, of the value of comparing how far a component of the
mixture has travelled in relation to how far a component of the mixture has travelled in relation to
how far the solvent utilised has travelled. The retention factor is calculated by dividing the distance
travelled by the substance by the distance travelled by the solvent. Due to the fact of the substance
unable to go further than the solvent utilised, the Rf value must always be less than one.



Due to the general attraction between the stationary and mobile phases, various compounds have
varying distances. Substances are distinguished by two characteristics: molecular mass and polarity.

- The molecular mass of a substance influences its travel distance- the slower it travels with
the solvent, the relatively larger it tends to be. This concludes to the solvent travelling a less
distance up the stationary phase.
- The polarity of both the content- the stationary phase and the mobile phase is the second
component that defines the distance travelled by a compound, since what is polar affects,
the distance travelled. Whereas, if the stationary phase or the mobile phase is polar and the
substance is polar, resulting in the substance to start climbing further up the stationary
phase.

, Different Types of Chromatography
Both thin- layer and paper chromatography serve in using a solvent to carry the components present
in the test sample, through a stationary phase. The stationary phase in paper chromatography is the
filter paper whereas in thin layer chromatography, the stationary phase is the thin layer of silica on
the TLC paper.

The chromatography and thin- layer paper serve in using a solvent to transport the components
contained in the test sample through a stationary phase. The filter paper is the stationary phase in
paper chromatography. Whereas the thin coating of silica on the TLC paper is the stationary phase in
TLC paper.



Paper Chromatography of Extracted Plant Pigments
Paper chromatography entails inserting paper labelled with an unknown, such as plant extract
(spinach in this case), inside a beaker with a specified solvent. The dissolved colours are picked up by
the solvent as it travels up the paper. Since the pigments are not all equally soluble, they are
transported at different speeds.



Equipment Used for This Practical

 Plant Leaves: Spinach
 Paper
 Universal Bottle and Lid
 Mortar And Pestle
 Propane
 Sharp Scissors
 Forceps
 Ruler and Pencil
 Capillary Tube
 Running Solvent made up of a 5:2:2 mixtures (by volume): Cyclohexane, Ethyl Ethanoate and
Propane labelled
 250cm^3 Beakers



Risk Assessment

Hazard Risk Safety Action Risk Level
Precaution