required practical 7 Flashcards
use of chromatography to investigate the pigments isolated from leaves of different plants, eg leaves from shade-tolerant and shade-intolerant plants or leaves of different colours
1
Q
what is the purpose of chromatography?
A
to separate different components in a sample
2
Q
state the factors affecting the rate of migration of different pigments
A
solubility, mass and affinity to the paper
3
Q
method
A
- draw a straight line in a pencil approximately 1cm above bottom of filter paper
- cut section of leaf and place in a mortar, add 20 drops of acetone and use pestle to grind sample and release pigments
- use capillary tube to extract pigments and blot onto pencil line
- suspend paper in solvent so liquid does not go above pencil line until solvent is almost as top of paper
- remove paper and use pencil to mark where solvent moved up to
- calculate Rf value for each spot at centre
4
Q
Rf value formula
A
distance moved by pigment/distance moved by solvent
5
Q
what is the purposeof finding the Rf value?
A
can be compared to standard value in database to identify the pigment
6
Q
how does affinity affect movement?
A
the lower the affinity, the higher pigments travel
7
Q
how does solubility affect movement?
A
the more soluble, the higher pigments travel
