Making 25 mM Tris-phosphate Buffer (pH 7.8)

[sotellme]

how can i make this buffer? i know how to make Tris- HCl buffer, but how about this one? what is the acid and base here?

25 mM Tris-phosphate (pH 7.8)

any ideas?

thanks.

 

[iansmith]

25 mM Tris-base
25 mM Phosphate or phosphoric acid

Adjust the pH to 7.8 with the phosphoric acid

 

[sotellme]

i thought this method is used for only conjugate pairs. Tris-base
and phosphoric acid are not conjugate of each other, are they?

thanks.

 

[Moonbear]

This is a new buffer to me (I've heard of both tris and phosphate buffers and use them regularly, but never heard of combining the two). What are you using it for (or what is it claimed to be used for)? How well does it buffer? What's the advantage of using this over just a tris buffer or phosphate buffer?

 

[iansmith]

i thought this method is used for only conjugate pairs. Tris-base
and phosphoric acid are not conjugate of each other, are they?

thanks.

I don't know, I am not a biochemist. It is how most people go about it.


Moonbear,

Tris-Phosphate when EDTA is added can be used in gel electrophoresis.

 

[sotellme]

i just don't know how can 25 mM Tris-base added to 25 mM phosphoric acid and still we get 25mM buffer. won't the concentration of each of the solutions change?

 

[Moonbear]

i just don't know how can 25 mM Tris-base added to 25 mM phosphoric acid and still we get 25mM buffer. won't the concentration of each of the solutions change?

I'm not sure how Tris and Phosphoric acid interact, but they must in some way or it wouldn't be a good buffer. So, in general, if you add 25 mM of A and 25 mM of B, you get 25 mM AB. If they don't interact (which wouldn't make sense given the purpose), you'd still have a solution of 25 mM of A and 25 mM of B; in other words, if there was no reaction/interaction between the two, adding B would have no effect on the concentration of A in your solution.