pH and temperature

Changes in pH due to temperature change

Water dissociate less at lower temperature

--> [H+] decrease as temperature lowered

--> pH increase as temperature lowered

 

Magnitude of change in pH

Rosenthal Correction Factor

• Change in pH = 0.015 pH units per degree C change in temperature

Therefore,

If pH=7.36 at 37C

--> at 34C, pH=7.405

 

Neutrality

At 25C, when [H+]=[OH-]
--> pH = 7.0

At 37C, when [H+]=[OH-]
--> pH = 6.8

 

Alpha-stat hypothesis

The degree of ionisation (alpha) of the imidazole groups of histidine in intracellular proteins remains constant despite changes in temperature

Widely accepted

pH-stat hypothesis

pH should be kept constant (at 7.4) despite changes in temperature