Why you directly not measure the pH of organic solvent?

Answer 1

pH is defined only in diluted aqueous solutions. The pH scale, 0 - 14, comes from the dissociation of water (Ka = 10-7). In non-aquous solutions there is no water so this scale is not valid. The only way for direct pH measurement is using a normal pH sensitive electrode (glass, ISFET, enemal, ...) and use a selective electrode sensitive to other compounds in the solution (salts, ions, ...) wich are not affected by pH change.

Answer 2

pH measurements are typically done in aqueous solutions because they require water to function properly. Organic solvents do not contain enough water for accurate pH measurements, as they can interfere with the electrode's response and affect the reading. Additionally, pH is a measure of hydrogen ion concentration, and organic solvents do not contain enough free protons to give a meaningful pH reading.