chlorophyll chromatography RP
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6 Terms
how do you calculate the Rf value?
Rf value = distance travelled by pigment ÷ distance travelled by the solvent
what determines the distance travelled by a spot in TLC? (1)
the affinity for the stationary phase / balance between solubility in mobile phase and retention by stationary phase
why must the origin line be drawn in pencil not pen?
ink from the pen would dissolve in the solvent and run
why should you draw a line where the solvent reaches immediately?
the solvent evaporates rapidly, so the end position isn’t visible shortly after the experiment
why should you measure the Rf value from the middle of the pigment mark?
the pigment mark is spread out
by measuring from the middle position each time it’s a way to standardise the measurements you’re taking
to allow comparisons
why should you make sure your chromatography paper is vertical and straight?
so the pigments move straight up the paper to avoid them running off the side and/or being washed off
Note 
Flashcards (28)