By Anonymous on Tuesday, June 29, 2004 - 11:24 pm:

Hi,

I understand that Amitriptyline is usually used as the probe to measure the silanol acitivity of silica based RP column at pH7. My question is if a primary amine, say benzylamine, can be used as the probe for silanol activity instead of Amitriptyline.

Can anyone comment on this? Thanks

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By RH on Thursday, July 1, 2004 - 09:16 am:

You can certainly use benzylamine for such a test procedure. There are just differences in what different test compounds tell you: e.g. if you compare the elution of phenol and pyridine, this gives you are very good idea of silanol activity as the elution order changes with silanol activity. The same is true for aniline/phenol, but aniline has a pKs of 4.5 ("mild" test) and the pKs of benzylamine is 9.3. So benzylamine is even completely retained on very silanophilic phases.Propranolole with a pKs of 9.6 is even harder to handle for phases........