Stability of sodium carbonate buffer

[Stacy Ferguson]

In article <1140553507.035106.202350 at o13g2000cwo.googlegroups.com>,
 "Susan Hogarth" <hogarth at gmail.com> wrote:

> I've been told that sodium carbonate buffers are stable only for
> 'weeks'. What happens to them, and what does 'weeks' mean? Two weeks?
> Twelve weeks?
> 
> - Susan

Bicarbonate breaks down to CO2 and water. While this is reversible, CO2 
doesn't stay in solution easily (if it did, you could just leave an open 
bottle of Coke in the fridge indefinitely) and that throws off the 
equilibrium. When I'm using carbonate buffers frequently, I just have a 
fresh batch made every 1-2 weeks. 

Stacy