Paper Chromatography - Investigating the Composition of Ink

in this experiment we will investigate

the composition of inks using paper

chromatography firstly we must define

our origin by drawing a line using a

ruler roughly 1 centimeter up from the

bottom of the chromatography paper this

must be done in pencil as the pencil is

insoluble in the water solvent we will

then define the area in which we will

place our inks and label their

respective colors following this we will

place a concentrated spot of our soluble

inks at each of the defined areas the

spot should be placed a reasonable

distance apart as during the experiment

the colors can tend to run and this will

prevent inaccuracies during the results

analysis we will measure a small volume

of the water solvent into a beaker

this must be shallower than the 1

centimeters R which we place our origin

line to prevent the chromatography paper

falling over during chromatography

analysis we can place a paper clip at

the top of the piece of chromatography

paper and use this to hook to the top of

the beaker during chromatography once

the paper is placed into the solvent

chromatography will begin it is vital

that the solvent does not pass the point

at which the inks were placed on the

origin line as at this point the

solvents would dissolve any of the

soluble inks that were on the line this

time-lapse video shows how the inks are

separated over a period of 10 minutes

once the inks

thirds of the way of the paper you

should remove the paper and allow it to

dry using a pencil you should now label

your solvent front this is the point at

which the water solvent moved off the

paper and stopped

our chromatogram is now ready for

analysis to analyze this we need to

determine the RF values of the spots to

calculate the RF value we use the

equation distance at a spot traveled

divided by the distance of the solvent

traveled these values can be determined

using a ruler and measured directly on

the chromatogram for each of the

different colored pigments we take the

peak point which is risen up the

chromatography plate

with our values determined these can

then be used to calculate the RF value

for a particular spot these can then be

compared against a reference spot or

other spots in the chromatogram sample