An excellent reference to general chemistry lab techniques can be found at the University of Wisconsin-Madison's GenChem Pages .
Paper chromatography is one of their documented techniques.
As the page describes, this method is good for determining the purity of substances. First you should know that the technique requires the materials studied to be dissolved. This can be tricky with vitamin tablets because they are essentially solid blocks. An easy way to get around this is to grind up the each vitamin tablet. This mimics the chewing process, but not the digestive process.