Anybody have a good suggestion for a low cost, relatively inert fluorescent marker that could be added in small amounts to a raw material and thus used to quantify that raw material level in a finished product by HPLC-fluorescence?

The choice of a fluorescent "tag" for your compound would depend on the reactive sites on your compound (i.e., an amine, a carboxylic acid, a thiol, etc.). There are may good derivitization approaches you can consider that add fluorescence detectability to may different reactive sites. I would suggest you consult a reference text titled "Handbook of Analytical Derivatization Reactions" by Knapp, Daniel R. (Wiley-Interscience Publication), which discusses each method in detail.

I was thinking of an unreactive fluorescent material which could simply be mixed in at a small amount, and later quantitated.

Dear Anonymus;

Is it possible you could use Ce+3 ion?, this is relatively non-reactive and it can be easily detected fy fluorescence. However, I would be cautious about adding anything to a raw material, the additive may end up in the finished product.

Benjamin

Try some quinine. (They put this in tonic water.) You should be able to see this down below the ppm level. Let us know how you make out.