Apparently this did not propogate from the news server to which I
posted it
originally.
In article <1157020009.287991.209120 at b28g2000cwb.googlegroups.com>,
pawel.stocki at ncl.ac.uk wrote:
> Does anyone have some experience in using ammonium bicarbonate buffer
> for gradient elution from Q-Sepharose or other IE? I would like to use
> it instead of NaCl gradient. The sample will be subjected for further
> MS analysis that is why I would like to use volatile salt. I'll
> appreciate any comments.
I've used ammonium carbonate/bicarbonate, pH 8 and 4 C for
purification of ATP/ADP/AMP mixtures both with QAE and with
DEAE media to prepare isotopically labeled mononucleotides
at high purity. Major considerations are:
1. Ammonium carbonate/bicarbonate, pH 8 must be fresh when used.
This is a volatile buffer and will decompose over several days
even at 4 C.
2. Don't go above 1 M bicarbonate.
3. Equilibrate the column with the bicarbonate buffer. As long as
it stays at pressure after equilibration, voids will not form.
4. After chromatography, re-equilibrate the column with a
non-volatile
buffer. This is a precaution to prevent void formation. I've
never had a problem with void formation, but this buffer could
form gas bubbles under some circumstances.
5. Rotary evaporation with methanolysis to decompose residual
ammonium bicarbonate works better than lyophilization (unless
the lyophilizer pump is protected with an ammonium trap) because
the ammonia tends to accumulate in the vacuum pump oil of the
lyophilizer. Typical rotary evaporation setups use either a
water vac or a diaphragm pump and these do not accumulate
ammonia.
6. Do not leave collected fractions of interest standing for
long periods after chromatography.
I hope this is helpful even after such a long time.
