Chromatography

AIM: To separate the coloured components present in a mixture of red and green ink by ascending paper chromatography and find their R_f values.

THEORY:

In this type of chromatography, a special adsorbent paper (Whatman filter paper) is used. Moisture adsorbed bon this Whatman filter paper acts as the stationary phase and the solvent acts as the mobile phase. The mixture to be separated is spotted at one end of the paper. This paper is then developed in a particular solvent by placing the paper in a gas jar, taking care that the spot is above the solvent. The solvent rises due to capillary action and the components get separated out as they rise up with the solvent at different rates. The developed paper is called a chromatogram.

R_f (retention factor) values are then calculated, which is the ratio of the distance moved by the component to the distance moved by the solvent front.

R_f = Distance traveled by the component
         Distance traveled by the solvent front

OBSERVATIONS AND CALCULATIONS: (ON THE BLANK PAGE, USING A PENCIL)

Component	Distance Travelled by Different Components	Distance Travelled by Solvent	Rf Value
Red	dr= 2cm	ds= 4cm	0.5
Green	dg= 3.8cm	ds = 4cm	0.95

RESULT: (ON RULED SIDE) –

The components of the mixture (red and green colour) separate in the form of spots lying between the origin line and solvent front.

R_f(green) = d_g/d_s = 3.8/4 =0.95

R_f(red) = d_r/d_s = 2/4= 0.5

Precautions

• The strip should not touch the walls of the jar.
• Do not disturb the jar after putting the strip in it.
• Allow the colours to seperate before pulling the strip out.

You can also get Class XII Practicals on Biology, Physics, and Physical Education.