By rao, sree on Wednesday, - 08:59 am:

why the Cyano column is unstable than C18 column

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By Chris Pohl on Tuesday, January 14, 2003 - 12:40 pm:

Cyano phases are definitely less stable than conventional C18 columns. This stems from 3 problems: first, the chemical bond to the silica surface is more accessible because of the small size of the ligand; second, the higher polarity of functional group improves the compatibility of reagents responsible for the hydrolysis process (i.e. acids or bases) which results in accelerated hydrolysis relative to more hydrophobic environments and third, the cyano group itself is not hydrolytically stable (although, this latter factor is probably not the predominant cause of capacity loss since hydrolysis of the cyano group under acid conditions is quite slow and proceeds rapidly only under alkaline conditions not generally utilized with silica columns). Agilent sells a product (Zorbax SB-CN) which reportedly has significantly improved hydrolytic stability do to the incorporation of two bulky isopropyl side groups into the cyano ligand. This helps restrict access to the cleavage site and renders the vicinity of the leakage to the surface more hydrophobic and thus less prone to hydrolytic attack.

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By Anonymous on Tuesday, January 14, 2003 - 07:03 pm:

hi
Chris

Thank you very much for replying to my question.