Quick UV Purity Question

[derboyl]

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

[Kostas Petritis]

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...

[derboyl]

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

[Kostas Petritis]

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

[derboyl]

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