Is Tris-HEPES a good substitute for Tris-HCl? - (Jan/16/2012 )

We routinely use Tris-HCl at pH8 for our buffers but we know that it's pH changes a lot with temperature. Recently I have noticed that a solution of 50mM Tris base and 50mM HEPES acid has a pH of 8.0 anywhere between 4-25C. Is it possible to replace Tris-HCl with Tris-HEPES if the chloride concentration is not an issue?

Besides, can someone tell me the correct way to calculate the buffering range/capacity of a mixed buffer like Tris-HEPES?

If you just want a buffered solution of a particular pH, then tris-hepes could work, as could phosphate buffered....