You can also try this technique at home using different coloured pens. If the inks are water soluble then water should be used as the mobile phase if the ink is permanent then methylated spirits can be used.

In this technique we introduce two new terms, stationary phase and the mobile phase. In this case the mobile phase is the solvent that is used to dissolve the inks as it rises up the paper. A stationary phase is what the ink and solvent particles have to move through, in this case it is the paper.

A number of pen dyes were analysed using this technique commonly known as thin layer chromatography. Each chromatogram is shown on the right below. Click on each chromatogram to see a more detailed image.

Calculate the Rf value of the red dye.