stable buffer at high pH - (Feb/24/2007 )
Hi
Does anyone know a buffer that would work fine at high pH?
I m currently using the Tris buffer for my enzyme activity test but when i add the media to the buffer, the pH drops (from 11 to 9)
I need another buffer that will be stable and work fine at high pH (ex. 11)
Thank you
Personally I don't know any. But here is a list I googled and copied from Sigma. Some of these may be of interest to you. Tris will not work. pKa = 8.06 This is way to low for the intend buffering at pH 11.
piperidine
pKa: 11.12
range: 10.5-12.0
borate
pKa: 9.23, 12.74, 13.80
range: 8.5-10.2
CABS
pKa: 10.70
range: 10.0-11.4
CAPS
pKa: 10.40
range: 9.7-11.1
carbonate (pK2)
pKa: 10.33
range: 9.5-11.1
methylamine
pKa: 10.66
range: 9.5-11.5
Does anyone know a buffer that would work fine at high pH?
I m currently using the Tris buffer for my enzyme activity test but when i add the media to the buffer, the pH drops (from 11 to 9)
I need another buffer that will be stable and work fine at high pH (ex. 11)
Thank you
Tris buffer work well in many cases. It has very high buffer capacity. What concentration do you use in your experiments. At what temperature do you measure pH? Note! pH of Tris buffer depends on temperature and may increase when temperature decrease ( up to 1 point of pH).
The rate of change of pH for Tris is -0.025 per degree increased temp.
the buffering capasity is not the point in this matter. If I understand this thread correctly, the intended pH of the buffer is pH 11.
This is far outside the range which tris can be used. Tris has a pKa value of only 8.06
Tris buffer work well in many cases. It has very high buffer capacity. What concentration do you use in your experiments. At what temperature do you measure pH? Note! pH of Tris buffer depends on temperature and may increase when temperature decrease ( up to 1 point of pH).
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thank you Perneseblue
Circlepoint, as i recall, the concentration of the Tris would be 100mM and i measure the pH at room temperature !
True, Tris has a wide range of buffering capacity. However, pernesblue's point still stands: even a buffer like Tris has its limits of usefulness. If your assay needs to be carried out at pH 11 or thereabouts, your results will be infinitely better if you use the most appropriate buffer.
For what it's worth, my suggestions are piperidine, then carbonate (a bit too close to its upper limit for my liking, but readily accessible).