[FDA_Mike]

I am analyzing a food product for coloring agents, and have come across an uncommon blue dye. 

I have uv-vis spectra in isopropanl & water for the acid, neutral and basic. 
Acid max at ~412nm,
Neutral max at ~638nm with rise ~412,
Basic max at ~630 with rise at ~412. 

Using a Silica 60 F254 TLC plate in a 1:1:1 Ethyl acetate:isopropanol:ammonium hydroxide system, it elutes with a pale blue color at Rf~0.32.

We have ruled out FD&C Blue 1 and 2 as well as Patent Blue V.

Any ideas?

[MOTOBALL]

Synthetic dyes, such as your 3 food dyes, are often accompanied by homologues. 

You might suspect a molecule that lacks one (or more) of the -SO3 groups of FDC1 and FDC3; also a molecule that has an -NMe group rather than -NEt in FDC1, etc.

I'm not familiar with the UVmax values of these materials, but do your UVmax values correlate with FDC 1/2 or patent blue V ??
 
You should ultimately go to LC-ESI/MS for ID.

Motoball