Question: what are the requirements of a good buffer?
Answer: A pKa between 6 and 8. ... 
Solubility in water. ... 
Exclusion by biological membranes. ... 
Minimal salt effects. ... 
Minimal effects on dissociation from changes in temperature and concentration. ... 
Well defined or nonexistent interactions with mineral cations. ... 
Chemical stability. ... 
Light absorption.