Urea determination in FIA mode by a newly designed urease-based biosensor

This article describes a new design of a urea biosensor developed by covalent immobilization of the enzyme urease on the top of a nickel-hexacyanoferrate-modified nickel electrode. The behavior of the electrode was described with respect to several experimental parameters in flow injection mode. Detection of urease-produced NH ion from parent urea at a working potential of 100 mV vs. a Ag/AgCl/2 M NaCl electrode showed linearity in the concentration range of urea in aqueous solutions from 10 μM to 10 mM. The influence of carrier electrolyte concentration, flow rate, and pH on the properties of the transducer were also examined. The selectivity recognition of the transducer was studied with respect to the influence of potentially interfering sodium and potassium ions. The electrode was tested over a period of 45 days. After this period, the biosensor lost only 20% of its sensitivity. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 266–271, 1999