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Making Tris Buffers of Various pH's by Mixing Tris acid and Tris Base - No HCL needed (Nov/25/2005 )

I had a recipe before for mixing tris acid with tris base in the right proportions to get 1 M Tris, pH 7.5. This is more convinenient than adding HCl, which I prefer to avoid using if possible.

I would like to make a chart for mixing tris acid and tris base to get various pH's commonly used in the lab, but cannot remember how to use the henderson-hasselbalch equation.

pH = pKa + log ([base]/[acid])

Could someone show me how to use this to make 1 M tris pH 7.5 using tris acid and tris base?

pKa = 8.214

MW of Tris Base = 121.136
MW of Tris Acid = 157.59

Taken from:
Tris Hydrochloride
Small White Flakes
Molecular Biology

Application: Tris Hydrochloride is a buffering medium for electrophoresis, molecular biology, and cell culture applications. It(Tris Acid) may be combined with Tris Base to simplify Tris buffer preparation.
Tris(hydroxymethyl)aminomethane Hydrochloride, Trizma* Hydrochloride
C4H11NO3.HCl, H2NC(CH2OH)3·HCl
F.W. 157.60


See the table here...

Looks like 127 g/L Tris-HCl, and 23.6 g/L Tris-OH for pH 7.5 at 25°C.


In the printed edition of theSigma catalog (p2026 edition 2004-2005, but I can't find it on their website) at the page for Trizma you will find a table that just gives the proportion for this kind of mix at different temperatures for a 0.05M solution.


QUOTE (Canalon @ Nov 26 2005, 03:53 PM)
...but I can't find it on their website...

Click the link I provided above for Art_Vandelay... biggrin.gif


QUOTE (HomeBrew @ Nov 26 2005, 09:17 AM)
See the table here...

Looks like 127 g/L Tris-HCl, and 23.6 g/L Tris-OH for pH 7.5 at 25°C.

Thanks HomeBrew. That's exactly the recipe that I used to use.


1 M TRIS pH 7.5 (1 L)

TRIS HCl 127 g
TRIS Base 23.6 g

Add dH2O to bring final volume to 1 liter.



You can also use the Buffer design web page of Rob Beynon (