phosphate buffer.. - na/k/na-k? differences? choice? better? (Dec/27/2006 )

hiyaaaaaaaa!
a very simple question..
if i were to with a phosphate buffer pH~7.0.. which buffer shud i choose?
a sodium phosphate? potassium phosphate? or a sod-pot phosphate?

how're these different in terms of their efficiency or anything??
thankyaaaaaaaaa!;)

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your choice of cationic version depends on what you like to do; Pi-buffers are classically used in physiology which means treating cells, tissue or organs; high K+ outside a cell has different effects compared high Na+; if you do not work physiologically prefer Na-Pi buffer because cytoplasm and its molecules are adapted to higher conc of Na+ than of K+; if you work with enzymes which depend on K+ add traces of K+ (PBS also contains traces of K+)

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if it is for chromatography (as indicated by your other post) and if you are running the column in the cold and if you are using a relatively high concentration of phosphate (or a gradient of phosphate or potassium chloride) then you may want to use potassium phosphate (it won't crystallize in the cold as sodium phosphate will). if you are using a sodium chloride gradient then use sodium phosphate.

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