Paper chromatography
Method overview
Draw a pencil baseline, place small concentrated spots, stand paper in solvent below the baseline, cover, allow solvent to rise, remove before the top, mark solvent front immediately, dry and calculate Rf.
Apparatus set-up
Diagramchromatography paper; pencil; ruler; capillary tubes; solvent; beaker with lid; reference dyes
Independent variable
sample identity or solvent
Dependent variable
number/position of spots and Rf values
Control variables
baseline height; solvent depth; paper; temperature; spot size
Apparatus
chromatography paper; pencil; ruler; capillary tubes; solvent; beaker with lid; reference dyes
Safety
Wear eye protection; some solvents are flammable/irritant; use ventilation and no flames.
Scientific rationale
Pencil is insoluble; baseline must be above solvent; lid reduces evaporation; components separate because of different affinities for mobile and stationary phases.