Metal ions can be separated by paper chromatography through a process similar to
the one you used to separate food dyes. However, the metal ions are not as
distinctly colored as the food dyes, so often an additional step is needed where
the developed paper is treated with a chemical agent that will make the metal ions
appear visible.
The table below gives some data that was obtained running both some known metal
ions and an unknown sample containing one or more metal ions.