Chromatography Forum

Hello,

Im too far out of collage to remember but does anyone know is it possible that one molecule/compound can give two UV responses when running a DAD.
If the molecule has more than one uv chromophore will it give two peaks for same retention time but @ different wavelenghts (220&254nm)?

The reason i ask is my new USP vitamine std is giving just that. It should be pure.

many thanks,
derek

Short answer is yes. Maybe you should have a look at the UV spectrum of your compound by doing a scan to see where it absorbs...

hello,

Thanks for that, i did in fact run a scan at the time and got two responces for the USP vitamin std i was running, i assumed the std was pure and was surprised to get a second response.

Have you seen this behaviour before? i have been running larger more complicated molecules that give one abs in scans!

perhapse it has to do with my detector settings??

thanks,
derek

It will purely depend on the number and type of chromophores that you have in your molecule. For a back to the basics (since you are too far out of college) I suggest the link below:

The UV-Visible Absorption Spectra section should reply all your questions (not only about the number of UV "responses" but why they absorb at the specific wavelengths etc).

http://www.cem.msu.edu/~reusch/VirtualT ... ectrum.htm

Goodman Kostas!
that link was very helpful, i had forgotten a lot of that stuff, but its good to know my instints are still healthy after all these years!

many thanks,
derek