calculation of rf for maddar & turmeric
DESCRIPTION
Calculation of rf for maddar & turmeric with TLC methodTRANSCRIPT
Experiment No.: 0
Experiment Name: Calculation of Rf for madder & turmeric.
Introduction:
To calculate Rf of Madder & Turmeric we need TLC
methods. TLC means Thin Layer Chromatography, which
is classified in chromatography section of chemistry.
Chromatography comes from Greek words chroma
(means color) and graphein (means to write). To separate
non-volatile mixtures is the main criteria of TLC. There are
two phase in TLC: stationary phase & mobile phase.
Stationary phase is a sheet of glass, plastic, or aluminium
foil, which is coated with a thin layer of adsorbent
material, usually silica gel, aluminium oxide, or cellulose
and mobile phase is a solvent or solvent mixture is drawn
up the plate via capillary action.
The retardation factor (Rf) is defined as the fraction of an analyte in the mobile phase of a
chromatographic system like TLC method. The retardation factor (Rf) is defined as the fraction
of an analyte in the mobile phase of a chromatographic system.
𝑅𝑓 =𝑥
𝑦
Here. 𝑅𝑓 = Retardation factor
𝑥 = distance traveled by the compound on mobile phase
𝑦 = distance traveled by the solvent front on stationary phase
Figure 2: Development of a TLC plate, a purple spot separates into a red and blue spot (courtesy: wikipedia.com)
For example,
If a compound travels 2.1 cm and the solvent front
travels 2.8 cm, the Rf is 0.75.
Figure 1: Separation of black ink on a TLC plate (courtesy: wikipedia.com)
Figure 3: Example of retention factor (courtesy: gxnu.edu.cn)
Objective:
To know About Thin Layer Chromatography (TLC) & its mechanism.
To know About Chromatography.
To know about Retention Factor (Rf).
To calculate Rf of madder and turmeric by TLC method.
Apparatus:
o TLC plates
o Pencil
o Ruler
o Solvent
o Pipettes
o Pasteur pipettes
o Beaker
o Gas Burner
Procedure of TLC in our Lab:
Step 1: Prepare the developing container
The developing container for TLC can be a specially
designed chamber, a jar with a lid, or a beaker with
a watch glass on the top. Pour solvent into the
chamber to a depth of just less than 0.5 cm.
Step 2: Prepare the TLC plate
TLC plates used in the dyeing labs are purchased as
20 cm x 20 cm sheets by our Chairman Sir. Each
large sheet is cut horizontally into plates which are
5 cm tall by various widths; the more samples I
planned to run on a plate, the wider it needs to be.
Then we cut the 20 cm x 5 cm TLC plate with three
equal part for three group.
Measuring 0.75 cm from the bottom of the plate.
Using a pencil, we draw a line across the plate at
the 0.75 cm mark. This is the origin: the line on
which I would spot the plate. Taken care not to
Figure 4: Apparatus (courtesy: google.com)
Figure 5: Developing container (courtesy: orgchem.colorado.edu)
Figure 6: Prepare the TLC plate (1) (courtesy: orgchem.colorado.edu)
press so hard with the pencil that you disturb the
adsorbent. Leave enough space between the
samples so that they do not run together; about 4
samples on a 5 cm wide plate is advised. Also we
give another mark on the upper side at 0.50 cm
which is measuring from upper side.
Step 3: Spot the TLC plate
If the madder or turmeric is not already in solution,
dissolve about 1 mg in 1 mL of a volatile solvent
such as hexanes, ethyl acetate, methylene chloride
or ethanol. As a rule of thumb, a concentration of
1% usually works well for TLC analysis. If the sample
is too concentrated, it will run as a smear or streak;
if it is not concentrated enough, you will see
nothing on the plate.
To obtain a micro capillary on TLC plate we need
small dot on TLC plate. In the labs, we make Pasteur
pipettes. Dip the Pasteur pipettes into the solution
and then gently touch the end of it onto the proper
location on the TLC plate. Shouldn’t allow the spot
to become too large - if necessary, we could touch
it to the plate, lift it off and blow on the spot. If we
repeated these steps, the wet area on the plate will
stay small.
Step 4: Develop the plate
Placed the prepared TLC plate in the developing
beaker, covered the beaker with the watch glass,
and leave it undisturbed place. The solvent will rise
up the TLC plate by capillary action. Make sure the
solvent does not cover the spot.
Allow the plate to develop until the solvent is about
half a centimeter below the top of the plate.
Figure 7: Prepare the TLC plate (2) (courtesy: orgchem.colorado.edu)
Figure 8: Turmeric Solution (courtesy: orgchem.colorado.edu)
Figure 9: Pasteur pipettes dipped in solution (courtesy: orgchem.colorado.edu)
Figure 10: Develop the TLC (courtesy: orgchem.colorado.edu)
Removed the plate from the beaker and
immediately mark the solvent front with a pencil.
Allow the plate to dry.
Step 5: Visualize the spots
If there are any colored spots, circle them lightly
with a pencil. If the TLC plate runs samples which
are too concentrated, the spots will be streaked
and/or run together. If this happens, we would
have to start over with a more dilute sample to
spot and run on a TLC plate.
Step 6: Calculating Rf
Now we were measuring the distance traveled by the madder or turmeric on mobile phase
and distance traveled by the solvent front on stationary phase of TLC plate for calculating the
retention factor of madder or turmeric. And put that value in required equation which is
describe in introduction.
Our Lab Sample:
Figure 11: Visualize the spots (courtesy: orgchem.colorado.edu)
Figure 12: Image of Lab Sample for testing madder & turmeric Rf
Conclusion:
This test is very important for dyeing because to find out the new color of chemical by testing
on TLC plate. In this experiment the madder have lower Rf factor then Turmeric which is better
for dyeing then turmeric dyeing. So this experiment also important for comparing the color
fastness of material. At last we say that this experiment is very important for basic
acknowledgement of TLC method, Rf for Dyeing.
Reference:
www.wikipedia.com
www.google.com
www.orgchem.colorado.edu
www.gxnu.edu.cn