Table 1 Raw date - distances moved by the photosynthetic pigments and by solvent during 3 trials.
The pigments can be identified by their colors and Rf values. In the table above the names of pigment are written as the colors in all three attempts matched with original pigments’ colors.
To get Rf value the calculation is: Rf = a/b where -
a = distance moved by pigment from its original position;
b = distance moved by solvent from same position.
The calculations made to convert raw date into Rf value: (([1] + [2] + [3]) / 3) / [4]
Table 2 Calculation of the Retardation factor (Rf):
Conclusion and evaluation
Five pigments of chlorophyll were separated and identified by paper chromatography: Carotene (yellow), Phaeophytin (yellow-grey), Xanthophyll (yellow – brown), Chlorophyll a (blue – green) and Chlorophyll b (green). This shows that the plant (nettle), which was examined, can pursue photosynthesis by absorbing different wavelengths, as different chlorophyll pigments absorb different wavelengths. Hence nettle could grow and photosynthesize in different wavelength light.
The chart 1 implies that highest retardation factor is of the pigment carotene (0.94) and the lowest – of the pigment chlorophyll b (0.4). The approximate values differ from original ones only very little; therefore, it could be presumed that experiment was successful.
There are several limitations while doing this experiment that could affect final results. Firstly, the extraction of the nettle was made from nettle tea and it can not be clearly known if the tea does not have any impurities. The improvement would be to use a fresh plant. Secondly, then preparing a paper for chromatography, the paper can not be touched with fingers in order not to oil them, so this is quite difficult as the paper has to be measured, cut and stuck to rubber bung. In order to prevent from this, tweezers should be used. Thirdly, while making an extract, there are only a few moments until extract starts boiling thus enzymes could denaturate. To deal with this problem, accurate sample’s observations should be done; when bubbles start collecting on the beaker’s walls, immediately take it from heater. What’s more, kerosene must be put into boiling tubes and the walls can not be touched with it hence when putting a chromatography paper in it, it’s difficult not to make it oiled. To prevent from this problem, kerosene should be poured into boiling tube through one side of it and the paper should be put through another.
