Extraction of Plant Pigment

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Plant pigments consist of four main chemicals. These are Chlorophylls, The carotenoids, Anthocyanin and Betacaine. The aims of this experiment is to separate the plant pigment into different colours using solvents and column chromatography. The hypothesis of this experiment is that this plant pigment from spinach will contain the chlorophyll pigment or may contain the others too.

Chlorophyll a is the main component of the plant pigments. This is used for the most important process, Photosynthesis. Chlorophyll a makes up about 75% of the plant pigment. The other 25% is the chlorophyll b.

Figure 1: Chlorophyll a (http://brsmblog.com/wp-content/uploads/2011/12/0-chlorophyll-a-1024x735.jpg)

Figure 2: Chlorophyll b (http://patentimages.storage.googleapis.com/EP0071991B1/imgb0003.png) Chlorophyll a and b provide the green colour of the plants. They absorb most of the light required for photosynthesis. The Carotenoids

These pigments can be found in many fruits and vegetables. They are commonly the yellow and orange pigments.

Figure 3: The carotenoids (http://chemwiki.ucdavis.edu/@api/deki/files/7280/=Zeaxantina.jpg) Anthocynins
This pigment associates with the colours pink, red, mauve, violet and blue which are found in flowers, fruit and vegetables. These have a function in reproduction.

Figure 4: Malvidin present in grapes (http://www.friedli.com/herbs/phytochem/anthocyanins.gif)

The Visible Spectrum
The mixture of chlorophyll found in spinach absorbs many wavelengths of the visible light. The absorbance peaks ranges 400 – 500nm is the blue range and 600 -700 nm the yellow- red range. The two principles of this light absorption stated (Practical Skills in Chemistry, 2011) are: 1) the absorption of light is exponentially related to the number of the molecules of the absorbing solute that are encountered, i.e. the solute concentration. 2) The absorption of light is exponentially related to the length of the light path...
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