Differential flow injection potentiometry

A differential flow injection potentiometric method, with two different ion-selective electrodes placed in series, is described. The dispersed sample contacts successively the two electrodes. In this situation, for a certain time interval each ion-selective electrode performs a reference function towards the other, which in this time interval reacts with the sample. In this way nitrate and chloride ions, and nitrate and ammonium ions could be determined simultaneously with nitrate and chloride-selective electrodes, and with nitrate and ammonium electrodes, respectively. It is shown, that by means of the differential flow injection technique it is possible to determine the nitrate content with a relative error of 10%, when the chloride ion concentration is thousand times higher.