Date: Tue, 7 Jan 1997 12:54:16 -0500
Message-Id: <v01540b00aef7ec9180a3@[10.0.2.15]>
From: nestgrp@world.std.com (Amos Heckendorf)
Subject: Re: HPLC gradient (high pH)
To: Recipients of ABRF List <abrf@aecom.yu.edu>
>I am looking for an alkaline HPLC gradient that can be used on a Shodex
>RS reverse phase column. Any suggestions will be greatly appreciated.
Carolyn:
In general, when using _silica_ based columns at neutral to alkaline pH,
avoid inorganic salts. Use GOOD buffers like tris, or organic amines.
Kirkland has showed that phosphate, borate and inorganic salts promote
degredation of silica columns much faster than these other buffers.
However, for your Shodex RPC column, which I assume is polymeric not
silica, you could use 10 mM ammonium phosphate with 0.1M sodium perchlorate
at pH 7.0 or higher as "A", and 60% MeCN + "A" as your "B" buffer.
(Perchlorate, which is a choatrope won't promote adsorption from HIC
mechanisms like other salts would, and it is soluble in higher amounts of
MeCN.) Perchlorate disrupts H-bonds preventing aggregation and promotes
interaction with the bonded phase in a more monomolecular fashion, to
enhace selectivity as Mant and Hodges showed in a a comparison of
conditions with and without the perchlorate buffer in their J Chromatogr,
359, 507 (1986) paper, figure 2. You could of course use a simple
phosphate (TEAP or ammonium) without perchorate as a starting point.
I hope this helps.
Amos
Amos Heckendorf (nestgrp@world.std.com) 800-347-6378 ; 508-481-6223
The Nest Group , Value Added Resellers
HPLC Operating Instructions and Molbiol. Protocols on WWW URL=
HTTP://world.std.com/~nestgrp