Amperometric Determination of Urea Using Enzyme-Modified Carbon Paste Electrode

摘要

An amperometric biosensor based on carbon paste electrodes(CPEs)for the determination of urea was constructed by enzyme(urease/GL-DH)-modified method.Urea was hydrolyzed to NH_4~+by catalyzing urease onto the enzyme-modified electrode surface in sample solution.In the presence of alpha-ketoglutarate and reduced nicotinamide adenine dinucleotide(NADH),a liberated NH_4~+ produce to L-glutamate and NAD~+ by L-glutamate dehydrogenase(GL-DH).After the chemical reaction was proceeded,the electrochemical reaction was occurred that an excess of the NADH was oxidized to NAD~+.The oxidation current of NADH was monitored at +1.10 volt vs.Ag/AgCl.An optimum conditions of biosensor were investigated:The optimum pH range for catalyzed hydrolysis reaction of urea was pH 7.0-7.4.The linear response range and detection limit were 2.0 X 10~(-5)approx2.0 X 10~(-4)M and 5.0 x 10~6 M,respectively.Another physiological species did not interfere,except L-ascorbic acid.