[dbranch]

I resently made a Tris-EDTA buffer that is displaying an increase in pH as heat is applied. 5°C-->7.8, 25°C-->8.0, 37°C-->8.3. WWWHHHYYYY? To the best of my understanding, increased heat should increase ionization resulting inan increase in[H⁺] and a decrease in pH.

Help please, TIO

[Babcock_Hall]

By itself TrisH⁺ increases in pK_a as the temperature decreases, and ΔpK_a/ΔT is about -0.03 pH units per degree Celsius.  I would consider the possibility of an error in standardizing the pH meter, but I am just guessing.

[Mitch]

Right, this might be a pH meter issue. Do you observe the same issue with just water?

[jeffmoonchop]

I heard tris is dodgy with regular pH meters and should use Calomel ones. Anyone know anything about that?

[Babcock_Hall]

Buffers:  The Basics (RJ Beyond) mentions that not all electrodes are compatible with Tris, but it does not supply more information than that.

[Borek]

Question is whether it is a matter of electrode glass (kind of a sodium error) or a reference (which is in general hidden behind junction or two).