To separate a mixture of indicators/colours using paper chromatography

Theory

Paper chromatography is used to separate the individual component colours out of inks/indicators

Procedure

• Using a dropper, place a drop of the ink/indicator ̴2cm up from the bottom of the chromatography paper on a pencil line drawn

• Place the chromatography paper into a beaker with ̴1 cm of a suitable eluent (water/methanol)

• Leave for one hour

Result

As the eluent mobile phase moves up the chromatography paper, each component colour in the ink/indicators is selectively adsorbed and appears on the chromatography paper stationary phase at different times

What is the mobile phase and the stationary phase in paper chromatography?

Mobile phase: Liquid eluent/solvent

Stationary phase: Chromatography paper

Name a suitable solvent for paper chromatography/suitable mobile phase/suitable eluent

• Water

Note: If it is a water insoluble mixture to be separated, an organic solvent is used

Example: methanol

Why is the line drawn on the chromatography paper in pencil?

• Using a pencil avoids contaminating the results with other types of ink

Where should the pencil line be drawn on the chromatography paper? Explain why this is important.

~ 2 cm up the chromatography paper i.e. 1 cm above the level of solvent placed in the gas jar to avoid the solvent dissolving the ink before it moves up the paper