GAS-SENSING DETECTOR WITH INTERNAL NONACTIN BASED ISE FOR FLOW-INJECTION POTENTIOMETRIC DETECTION OF SUBSTRATES PRODUCING AMMONIA IN ENZYMATIC REACTION

Abstract

Ion-selective electrode with polymer membrane containing nonactin is employed for the potentiometric detection of ammonia produced in biocatalytic reactions. Elimination of interferences occuring in the presence of alkali metal ions can be achieved by covering a nonactin membrane with outer hydrophobic gas permeable membrane with a layer of internal solution between the membranes and a miniature reference electrode. Optimization of design of such a sensor for the enzymatic detection of substrates in flow-injection measurements with a large-volume wall-jet detector was carried out. Among experimental variables optimized were composition of a nonactin containing membrane, kind of gas permeable membrane, geometry of the sensor and composition of the internal solution.