[lorem]

I have a sample of protein which I would like to concentrate by lyophilization (freeze drying). I'm planning to use a ammonium bicarbonate solution as a solvent, as it decomposes to ammonia, carbon dioxide and water when lyophilized. The problem is that I would like to adjust the pH of the solution downwards. For this, I need an acid which which would be completely eliminated along with the ammonium carbonate during lyophilization. Would somebody have experience on matter?

[AWK]

What about acetic acid?