The Achilles´ Heel of Potentiometric Measurements, the Liquid Junction Potential

The mechanical design of the liquid junction and materials used for the construction of the potentiometric measuring cell are discussed. Single ion conductances at 37 °C for common ions in calibration solutions are presented and a calibrating solution without residual liquid junction potential when compared with blood plasma is proposed. A new salt bridge solution containing sodium formate, which eliminates the suspension effect during whole blood measurements, is also presented, as are results from a comparison on whole blood between the new salt bridge solution and the traditional KCI salt bridge solution.