POTENTIOMETRIC AND CONDUCTOMETRIC DETERMINATION OF AMMONIUM BY GAS-DIFFUSION FLOW-INJECTION ANALYSIS

Considerable enhancement of selectivity in the potentionmetric and conductometric determination of ammonium is provided by gas-diffusion separation in flow injection analysis. Ammonium and potassium selective liquid membrane electrodes can be used for determinations in the concentration range 10(-7)-10(-2) mol/l with high precision and fast sample throughput. No interferences are encountered in the presence of ionic species and molecules that likely adsorb when the sensors are in direct contact with the sample. The selectivity over volatile amines is enhanced due to kinetic discrimination. Conductometric detection is shown to be as sensitive as the potentiometric detection. A major advantage, however, is the linear rather than logarithmic relationship between concentration and conductivity.