AMPEROMETRIC BIOSENSOR FOR UREA

An enzyme electrode for the amperometric measurement of urea was prepa red by co-immobilizing L-glutamate dehydrogenase and urease onto an Im mobilon-AV affinity membrane attached to a glassy carbon electrode. Th e reduced nicotinamide adenine dinucleotide(NADH) was used as the elec troactive species. The electrochemical oxidation of NADH was monitored at +1.0 volt 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 approximately 3 min. and the optimum pH of the enzym e immobilized membrane was pH 7.4-7.6 (Dulbcco's buffer solution). It was stable for at least two weeks or 50 assays. There was no interfere nce from other physiological species, except from high levels of ascor bic acid.