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Flashcards in 2: Chromatography Deck (6):

How could we separate photosynthetic pigments?

with chromatography
- paper chromatography used in class
- thin layer chromatography is better


Describe method for chromatography (first 4 steps).

1. tear up leaf into small fragments
2. grind pieces of leaf with sharp sand and propanone to extract leaf pigments
3. transfer sample of extract to a watch glass
4. evaporate to dryness with hot air from hair-dryer


Describe method for chromatography (second 4 steps).

5. add a few drops of propanone to dissolve the pigments
6. build up a concentrated spot of pigment 10mm from the end of the strip of paper/TLC strip
7. suspend the strip in a tube with the base dipping into running solvent
8. remove the strip from the tube when the solvent has nearly reached the top (of strip)


What is the Rf value? Describe method for calculating Rf value.

Rf = ratio of the distance traveled by a compound to that of the solvent front

Rf = distance moved by spot (a pigment) / distance moved by solvent


Why do pigments separate in chromatography?

because of their varying solubility in the running solvent


State 4 main pigments and their approximate Rf values.

1. carotene (0.9)
2. chlorophyll a (0.65)
3. chlorophyll b (0.6)
4. xanthophylls (0.3-0.5)

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