RP 7 Flashcards
What does the rate of migration of each pigment depend upon?
affinity to chromatography paper , higher= shorter
mass
Why must the line be drawn using pencil?
not ink as soluble in water SO could interfere with results
Why must you measure from the centre of the pigments?
to standardise results
allows distances to be comparable
Why is the solvent front market immediately after?
solvent will evaporate quickly so hard to see the solvent front
needed to calculate Rf values
How to calculate Rf values
Distance moved by pigment/ solute
divided by
Distanced moved by solute
Usefulness of Rf values
A ratio that remains constant for each typeof pigment
same pigment may move different distances based on different solvents but Rf value always the same
allows for identification, Rf values looked up on a database to identify them
Key stages
Draw a pencil line
cut grind leaf, acetone
capillary tube dab pigment, centre of line
spend paper in solvent, ensure pencil line does not get submerged
allow time solvent run up
mark solvent front
pigments should separate out different spots different distances
measure distance traveled by each spot ( from centre)
calculate Rf values
