Chromatography Forum

dear friends...

Could you please shed some light on this?

I am really new to LC/GC.

I know that using the GC/MS it is possible to identify unknown compounds with the help of a spectra library (NIST), the mass spectrometer provides a spectrum of the compounds which shall be compared with those in the NIST, if it matches, great. But here comes the question:

How do we do this on a HPLC? The HPLC I use has a refraction index detector and a PDA detector (UV). What do I do once I got the spectra from these detectors?

Another question, if I can't identify the compounds, how will I say that peak A, B and C are water, methanol and ethanol, for example?

If I have a misterious liquid, how do I identify what is in such liquid using a HPLC?

Thank you very much.

"What do I do once I got the spectra from these detectors? " - PDA spectrum is not so rich in signals so you could say what compound is it just by looking at, it is really poor in information, but hey it's just a bit better than refractive index spectrum

"how will I say that peak A, B and C are water, methanol and ethanol, for example? " - you inject standard and compare if retention times are the same, to be more confident in thisiinformation you do the same using some orthogonal method, you can add comparing PDA of course

would be easier if you had MS

"If I have a misterious liquid, how do I identify what is in such liquid using a HPLC? " - HPLC is not some identification tool, it is a separation tool, but as I have written there are some clues you can use but only when you have a STD of what you are looking for

Thank you very much for your detailed explanation, really.