Measurement of pH and pNa in cells without a liquid junction.

A method for carrying out electromotive force measurements of pH and pNa in cells without a liquid junction is described. The method involves the use of two glass electrodes, one selective to H+ ions and the other to Na+ ions and it can be applied to different types of potentiometric determination. Values of pH and pNa thus obtained for different samples are collected and compared with those obtained using conventional methods. Potentiometric titrations can also be carried out using the proposed method. To verify that the method is suitable for equilibrium studies, the protonation constant of acetate was determined. The agreement between the value obtained and that determined by a conventional procedure was good, thus supporting the validity of the method in equilibrium studies.