tris HCL buffer

[Sumi Akagi]

Sorry, I'm a bit of a newbie when it comes to tris HCL buffer, but I have some questions:

I'm trying to make a tris HCL buffer of 1.2M with 10.5 pH. My preferred volume is 7.5 mL, and I know the amount of tris base (1.09g ) and HCl (3uLwith HCL being 37.2%(12.1M) )I need, but I don't know the amount of deionized water I need to dissolve the tris base in. Is it possible to use a recipe for 1L and add 800mL of deionized water or does that change the outcome for the tris HCL buffer?

[CharonY]

Generally speaking, I would advise to confer with supervisor regarding basic lab tasks. The reason for that is that you and your lab have to be in sync when it comes to basic procedures as miscommunication will jeopardize any analyses you want to do. 

Based on your question you might be a bit confused how molarities are calculated (i.e. your question regarding 1L water and changing it to 800 mL does not make much sense to me, especially if you want to make 7.5 mL of the buffer).

The other issue is that tris-base has a pKa of around 8. It is unclear how you want to reach a pH of 10.5, especially with HCl.

[John Cuthber]

25 minutes ago, Sumi Akagi said:

I'm trying to make a tris HCL buffer of 1.2M with 10.5 pH.

You can't.
Or, at least, you can't make a good buffer at pH 10.5 with Tris.

"

Buffering features[edit]

The conjugate acid of tris has a pK_a of 8.07 at 25 °C, which implies that the buffer has an effective pH range between 7.1 and 9.1 (pK_a ± 1) at room temperature."


From https://en.wikipedia.org/wiki/Tris