title: Amperometric determination of urea using an NADH-dependent coupled enzyme.
abstract: Enzyme electrodes for the amperometric measurement of urea were prepared by co-immobilizing l-glutamate dehydrogenase and urease onto an Immobilon-AV affinity membrane with attachment to a glassy carbon electrode. Reduced nicotinamide adenine dinucleotide (NADH) was used as the electroactive species. The electrochemical oxidation of NADH was monitored at +1.0 V vs. Ag/AgCl. The enzyme immobilized electrode was linear over the range of 2.0 x 10(-5) to 2 x 10(-4)M. The response time of the electrode was 3 min and the optimum pH of enzyme immobilized membrane was pH 7.4-7.6 (Dulbecco's buffer solution). It was stable for at least two weeks and 50 assays. There were no interferences from other physiological material, except for high levels of ascorbic acid.
authors.affiliation: Department of Chemistry, University of New Orleans, New Orleans, LA 70148, U.S.A.
authors.forename: G G
authors.initials: GG
authors.lastname: Guilbault
authors.forename: M L
authors.initials: ML
authors.lastname: Seo