Amino Acids in a dicarboxylic acid

[pkup]

Hi-
I am trying to find any amino acid impurities in a dicarboxylic acid. I'm using the Waters Accq-Tag system to derivatize the amino acids. But for some reason, when I run it on the HPLC, none of the amino acid peaks are showing up. When I run a standard amino acid mix without the dicarboxylic acid, all of the peaks are there. Could something in the dicaboxylic acid be interfering with the devitatization? Would I be better off trying a different derivatizing agent? Please let me know.

Thanks!

[pkup]

Just in case anyone cares or has a similar problem... we figured out that the pH of the solution was too low for the derivatization, so we added NaOH until it was closer to neutral.