Chemical Forums
Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: dbranch on May 17, 2019, 10:28:32 PM
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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
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By itself TrisH+ increases in pKa as the temperature decreases, and ΔpKa/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.
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Right, this might be a pH meter issue. Do you observe the same issue with just water?
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I heard tris is dodgy with regular pH meters and should use Calomel ones. Anyone know anything about that?
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Buffers: The Basics (RJ Beyond) mentions that not all electrodes are compatible with Tris, but it does not supply more information than that.
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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).