Separating mixtures using chromatography
Introduction
Chromatography is the method used in order to separate mixtures of chemical compounds.
Examples of uses of chromatography include drug testing, forensic testing, food testing
and the development of vaccines [1]. The way in which chromatography works is that there
is a stationary phase (The solid surface at which the substance and solvents travel on) and
a mobile phase (the solvent which carries the pigment.) As the solvent travels up the
mobile phase, the components of the mixture are either more attracted to the stationary
phase (e.g. paper) or the mobile phase (the solvent) this causes the different components
to separate out on different places on the stationary phase which, when visible, can be
measured to calculate the Rf value of the components in order to identify them. When
using pigments for chromatography e.g. ink or plant pigments.
How much the components of the mixture adsorp and desorb determine how the
components separate
Adsorption and Desorption
Adsorption
When a substance sticks to the surface of a material: Adsorption is when the forces
between the solute molecules and the surface of the stationary phase have a stronger
attraction than the forces between the solute molecules a strong attraction is the result of
bonds being made between the components of the substance and the stationary phase.
The stronger the attraction, the less it travels up the stationary phase. In chromatography
substances in the solution adsorp onto the stationary phase but each substance adsorps
by a different amount which results in the separation of the substances.
Desorption
Desorption is when the components of the mixture have a greater intermolecular
attraction to the mobile phase than the Stationary phase so they become unattached from
the stationary phase and spend more time in the solution.
, Chromatography in plants (spinach leaves)
Equipment
• Spinach leaves
• Solute (acetone)
• Magnesium sulfate
• Sand
• TLC paper
• Spatula
• Mortar and pestle
• Ruler
• Pencil
• A few Pasteur pipettes
• Acetone
• Propanone
• 250ml glass beaker
Introduction
Chromatography is the method used in order to separate mixtures of chemical compounds.
Examples of uses of chromatography include drug testing, forensic testing, food testing
and the development of vaccines [1]. The way in which chromatography works is that there
is a stationary phase (The solid surface at which the substance and solvents travel on) and
a mobile phase (the solvent which carries the pigment.) As the solvent travels up the
mobile phase, the components of the mixture are either more attracted to the stationary
phase (e.g. paper) or the mobile phase (the solvent) this causes the different components
to separate out on different places on the stationary phase which, when visible, can be
measured to calculate the Rf value of the components in order to identify them. When
using pigments for chromatography e.g. ink or plant pigments.
How much the components of the mixture adsorp and desorb determine how the
components separate
Adsorption and Desorption
Adsorption
When a substance sticks to the surface of a material: Adsorption is when the forces
between the solute molecules and the surface of the stationary phase have a stronger
attraction than the forces between the solute molecules a strong attraction is the result of
bonds being made between the components of the substance and the stationary phase.
The stronger the attraction, the less it travels up the stationary phase. In chromatography
substances in the solution adsorp onto the stationary phase but each substance adsorps
by a different amount which results in the separation of the substances.
Desorption
Desorption is when the components of the mixture have a greater intermolecular
attraction to the mobile phase than the Stationary phase so they become unattached from
the stationary phase and spend more time in the solution.
, Chromatography in plants (spinach leaves)
Equipment
• Spinach leaves
• Solute (acetone)
• Magnesium sulfate
• Sand
• TLC paper
• Spatula
• Mortar and pestle
• Ruler
• Pencil
• A few Pasteur pipettes
• Acetone
• Propanone
• 250ml glass beaker
