Why do you need to cover the beaker with a lid during paper chromatography?

Answer 1

During the development of a chromatogram, it is better to cover it with a beaker to prevent evaporation, which will affect the movement of the solute and solvent system. This will ensure that the chromatogram will develop properly.

Answer 2

For the chromatogram to develop properly and components to show the correct Rf values for the solvent [or solvent mix] used, it is essential that the chamber is saturated with solvent vapour. Why? Otherwise instead of moving up the base material [paper, silica gel etc] solvent will be evaporating along the whole lenght and at the solvent front. This will give inaccurate Rf values, so you must keep the top firmly on.

Common chromatogaph developers,like butanol:ethanol:ammonia 3:1:1 saturate the surrounding air pretty quickly, but if the top was left off, much of the ammonia would escape more rapidly than the butanol vapour [because its relative molar mass is only 17] and this would actually change the composition of the developing solvent moving up the stationary phase... another reason to keep it sealed!

Answer 3

Covering the beaker would just stop the solvent from evaporating away.

Answer 4

To prevent evaporation of the eluting solution (solvent) from the paper

Answer 5

to avoid evaporation of mobile phase and easily achieve total equilibration of the mobile phase inside.

Answer 6

The purpose is to avoid solvent evaporation.

Answer 7

blasly