Chromatography Forum

Does anyone work with amidopropyl dimethylamines and respective quaternized salts analysis? I have, recently, synthesized the compound stearamidopropyl dimethylamine, which I have to do a HPLC/CG analysis. Which conditions and column should I use?

Than you

The GC analysis would be hard, because the Stearamidopropyl dimethylamine have a very high boiling point, so you should have appropriate GC system and high temperature columns.

For HPLC I think i would go with C8 column. The Stearamidopropyl dimethylamine have long aliphatic chain so the interaction with stationary phase will be strong. Preferable use a column with very good endcaping (or other types of silica with very low silanols activities) to avoid peak tailing caused by the nitrogen atoms in the substance.

The C18 column will have more interaction with stationary phase than C8 column so the % of organic solvent should be much higher. Maybe the RP-amide column could give an interesting selectivity, something to try on.

Thank you, Kreall!

Could you give me some reference on endcapping, I am not familiarized with the term. Also, which detector should I use? I have been reading some journals which say that a UV detector wouldn`t work well.

Here are some references about columns:
http://www.lcresources.com/tsbible/16041998.pdf
http://www.sepscience.com/Techniques/LC ... nd-capping
http://www.lcresources.com/tsbible/21032003.pdf

also the whole page about HPLC trubleshouting is someting maybe you should look it to.
http://www.lcresources.com/tsbible/

I can't think why using UV detector is not a good idea for this substance. Maybe someone used a specific mobile phase with was not appropriate for UV detection. It is hard to me to say, I don't have much expierence with analysing surfactants.

The problem with UV detection is that with this compound you must use a low detection wavelength (something in the range 200-220nm) because there's no decent chromophore besides the carbonyl. Still, sensitivity will not be very good. At such a low wavelength you'll see all sorts of stuff included in your sample, so specificity might be a problem.
Doesnt' mean that it cannot work, though.

You are going to have two problems, severe tailing on RP columns and LOD/LOQ for your compounds. Mixed-mode might be a viable solution with UV or ELSD detection.
Something like these:
http://www.sielc.com/Application-Separa ... olumn.html

if you only care about hydrophobic quats, then this is your best approach:
http://www.sielc.com/Compound-Cetylpyridine.html

Thank you very much!