Metal-metal oxide enzyme electrodes for the determination of urea

Enzyme electrodes for urea assay based on metal-metal oxide (Sb, Bi, W, Ti + RuO₂) with urease immobilized in gelatin gel were examined. It was shown that the best electrodes were obtained for tungsten. The urea response of the electrodes was influenced by the pH and concentration of the buffer used. Increasing additions of inert salt (potassium chloride) change the pH characteristic of the tungsten electrode and buffer capacity, thus influencing the urea response of the electrode.