MEDIATED AMPEROMETRIC DETERMINATION OF AMMONIA WITH A METHANOL DEHYDROGENASE FROM PSEUDOMONAS SP AM-1 IMMOBILIZED CARBON-PASTE ELECTRODE

PQQ-dependent methanol dehydrogenase (EC 1.1.99.8) was immobilized ont o the surface of a carbon paste electrode by the cross-linking method and the electrode was covered with a porous polycarbonate membrane. An electrocatalytic steady-state current for the oxidation of methanol w as observed using this electrode in the presence of phenazine methosul phate as an electron transfer mediator and NH4Cl as an activator for e nzyme activity. The electrocatalytic current at +0.2 V vs. Ag/AgCl was analyzed. The properties of the electrode were examined for the deter mination of ammonia. The electrode responded linearly to ammonia in th e range of 3 to 60 mM. The assay took 40 to 50 s. The electrode was us ed repeatedly at room temperature for 15 days and retained 50% of its initial activity.