ENZYMATIC BIOSENSOR FOR UREA BASED ON AN AMMONIUM ION-SELECTIVE BULK OPTODE MEMBRANE

A urea biosensor with the enzyme urease entrapped in a photo-cross-lin ked polymer is described. The enzyme layer is placed on top of an NH4-selective optode membrane incorporating the ionophore nonactin and a hydrogen ion-selective chromoionophore. The immobilization was carried out under very mild conditions, so that the properties of the optode membrane remained unchanged. The short-term repeatability, dynamic res ponse, selectivity and the long-term stability of the sensor and the i nfluence of the buffer concentration are discussed.