Is it possible to inject a dark solution in HPLC? I mean, if a substance is dissolved, and it gives a dark red solution. Can it still be analyzed? Or would I have to extract those pigments first? Thanks all

I've injected samples that were blue because they contained a dye. I've also injected samples that were white-opaque, probably due to lipids content. They worked fine, but my detector is a triple-quad. If you use a guard column, and you're pretty sure that your sample is particulate-free (or you've filtered it), then you should be OK. Then the problem is whether you can separate your analyte from all that matrix background and detect it. I once had samples that were the color of red wine. Those didn't work out so well. :-)

I've analysed deep red and ink blue anthracycline drug solutions in saline without a problem - as MG said, as long as you have a particulate free solution you should be ok. Good luck :o)

Thanks. I'm using UV detection, so I was worried about that. I always filter before injection. I'll get an old column first just in case though. See what it does. Thanks again.

Should be no problem unless dye substances co-elute in your region of interest. Lots of dyes are complex sulfonic acid salts, and need a complex mobile phase to retain them, so I don't think you'll have any trouble at all.