Why is the baseline drawn in pencil in chromatography
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
