STANDARDIZATION OF POTENTIOMETRIC SENSORS IN TETRAHYDROFURAN

Dissociation constants of the strongest acids, perchloric acid, pK(a) = 7.57, trifluoromethanesulphonic acid, pK(a) = 7.83, and their tetrabutylammonium salts, pK(salt) = 5.65 and 5.37, respectively, and in addition the dissociation constant of tetrabutylammonium picrate, pK(salt) = 5.21 and lithium and sodium perchlorates, pK(salt) = 6.81 and 7.11, respectively, were determined conductimetrically in tetrahydrofuran. The overall dissociation constant of picric acid, pK(a) = 11.84, was evaluated by potentiometric measurements. The three acids studied allow easy standardization of potentiometric sensors in tetrahydrofuran, but standardization with picric acid is the least affected by changes in solvent composition and is proposed as a routine method.