Retention of small amine

[Patrik Appelblad]

Thunderbunny,

I've been in the lab to check up a few things. I chosed a similar mobile phase system to yours, but changed the THF to acetontrile, and as we do not have that little pyrrole hanging around, I took Imidazole, 1,2,3-triazole and 1,2,4-triazole as model compounds. With 97 % Acetontrile and ammonium formate you protonate Imidazole so that is easily retained. The other two had rather meagre retention though (K' in between 0.5 and 1). Switching to 0.2% Formic acid in the aqueous portion of the mobile phase increased the retention for the triazoles. Therfore my suggestion to you is to switch from the formate to formic acid. Your pyrrole had a pKa around 4, I believe, so Formic acid should definitely be enough to protonate the pyrrole and give you higher retention.

I'm although a bit worried that your other compounds will be tricky to retain in this system, maybe they are better chromatographed with an RP-system?

Please keep us posted with the progress. Personally I was very intrigued with this problem, and I hope my suggestion will help.
/Patrik

[SIELC_Tech]

We did a fast screening for this compound and got K'=10 (ten) on Primesep 100 column with ACN-water-phosphoric acid=50/50/0.1.

You can use short column (50 mm) and get retention of 5 minutes or so, on a longer column you have longer retention. If you decrease concentration of acid to 0.05 you will have retention of over 8 minutes even on 50 mm.

What is good about our approach is that if you have hydrophobic compounds they will retain too and you can easily control retention by amount of acetonitrile. Changing amount of acetonitrile will not affect retention of 1-methyl-1H-pyrazol-3-amine
I will post the link later.

regards,

Vlad