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