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[Protein-analysis] Re: Ammonium bicarbonate in IE chromatography

Dr Engelbert Buxbaum engelbert_buxbaum at hotmail.com
Sun Sep 3 22:09:50 EST 2006


Rhodobacter wrote:

> its better to dialyse or ultrafiltrate your sample after the IE 
> chromatography!
> Alternativly you can use a desalting column or ZIPTIPs (e.g. Qiagen).

All this works only for reasonably large sample molecules. Purification
of small molecules by IEC equires volatile buffers that can be removed
by lyophilisation.

> For most samples you need strong Ions in the IE chromatography. May be that 
> the carbonate degas as CO2 and you will get some bubbles in your column.

Probably not on the column, because of the high pressure there. But
storage of the buffer is not possible, and buffer decomposition can
occur in the fractions, leading to a shift in pH. This can happen also
during lyophilisation, one reason why I have stopped to use acetate or
formiate based buffers, even though they are often recommended (the acid
goes of slower than the ammonia or trimethylammonia and makes the sample
strongly acidic). 


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