Buffers for biological systems should satisfy the following requirements:
A pKa between 6.0 and 8.0
High water solubility and minimal organic solvent solubility
Exclusion by cellular membranes
Minimal salt interactions
Minimal interactions between buffer and critical reaction components
Should not absorb light in the visible or UV spectrum
Stable and resistant to enzymatic degradation
Minimal changes on dissociation from changes in concentration and temperature
Easy to manufacture and purify
Cost-effective