AN ENZYME SENSOR FOR UREA BASED ON CONDUCTIVITY MEASUREMENT

An enzyme-based sensor for the determination of urea is described The system uses urease immobilized to porous glass and conductivity electr odes to measure the increase in conductivity of the sample solution re sulting from hydrolysis of urea into charged products. A linear relati onship between the changes in conductivity and urea concentrations was obtained with concentration up to 8 mM (correlation coefficient, r = 0.996 +/- 0.002). The response of the enzyme column was stable when us ed intermittently for up to 48 days or > 60 h operation time. Good agr eement was obtained when the concentrations determined by this system were compared with the diacetylmonoxime colorimetric method (r = 0.994 ).