Making 25 mM Tris-phosphate Buffer (pH 7.8)

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Discussion Overview

The discussion revolves around the preparation of a 25 mM Tris-phosphate buffer at pH 7.8. Participants explore the components required for this buffer, the interactions between Tris and phosphoric acid, and the practical applications of this buffer in laboratory settings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the preparation of a Tris-phosphate buffer, specifically asking for clarification on the acid and base components involved.
  • Another participant suggests using 25 mM Tris-base and 25 mM phosphoric acid, indicating that the pH should be adjusted to 7.8 with phosphoric acid.
  • Concerns are raised by a participant regarding the appropriateness of using Tris-base and phosphoric acid together, questioning whether they constitute a conjugate pair.
  • A participant expresses unfamiliarity with the Tris-phosphate buffer, asking about its applications and advantages over using separate Tris or phosphate buffers.
  • There is confusion about how combining 25 mM Tris-base with 25 mM phosphoric acid results in a 25 mM buffer, with participants questioning the concentration changes that may occur upon mixing.
  • Another participant speculates on the interaction between Tris and phosphoric acid, suggesting that if they do interact, it would be necessary for the buffer's effectiveness.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of using Tris-base and phosphoric acid together, with some questioning the concept of conjugate pairs. There is also uncertainty regarding the concentration changes when mixing the two components, indicating that the discussion remains unresolved.

Contextual Notes

Participants highlight limitations in their understanding of the interactions between Tris and phosphoric acid, as well as the implications for buffer preparation. There are also unresolved questions about the buffering capacity and practical applications of the Tris-phosphate buffer.

sotellme
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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.
 
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25 mM Tris-base
25 mM Phosphate or phosphoric acid

Adjust the pH to 7.8 with the phosphoric acid
 
i thought this method is used for only conjugate pairs. Tris-base
and phosphoric acid are not conjugate of each other, are they?

thanks.
 
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?
 
sotellme said:
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.
 
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? :eek:
 
sotellme said:
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? :eek:

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.
 

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