food colouring for chromatography

Hi,

We are experiencing a spot of bother with food colourings which in the past have split nicely when spotted on a filter paper and water is drawn up though it.

Dr. Oetker seems to have changed his recipe to "natural" ingredients which, for our purposes, are naff

Got any suggestions?

I am currently playing around with slightly watered down colourpaste, used to colour fondant icing, for use in chromatography. Although more expensive initially than standard food colouring (approx £2.25 each)it does last for ages, we are still using some after 3 years. It is available from amazon & ebay and probably other sites or cake decorating outlets.The primary colours come out solid but the violets, oranges etc do give nice separations. The liquorice black, however, doesn't.

One of our lessons requires 5 black pens each of which need to give a different chromatogram, we have ended up making our own combinations of colour from the primary colours and added the 'liquorice black' so it looks black on paper, but each one gives a different result.

Hope that helps

thanks
we did wonder if mixing them might be the answer
just a bit time consuming

can't get the hang of this font thing!!!!!