Amperometric Determination of Urea Using Enzyme-Modified Carbon Paste Electrode

Abstract

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 α-ketoglutarate and reduced nicotinamide adenine dinucleotide(NADH), a liberated NH 4 + produce to L-glutamate and NAD + by Lglutamate 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 × 10 −5~2.0 × 10 −4 M and 5.0 × 10 −6 M, respectively. Another physiological species did not interfere, except L-ascorbic acid.

Detection of Urea in Human Blood using Graphene-Based Amperometric Biosensor

“…The optimum pH (pH 7) obtained in this experiment was consistent with the previously reported studies. 29,30 Settling time optimization.-Urea determination is based on the hydrolysis of urea by the enzyme urease. After an ideal settling time (chemical reactions reach equilibrium), we measured the amperometric current by oxidizing the excess NADH at a fixed potential.…”

“…8,9 The urea hydrolysis process by the urease enzyme serves as the basis for electrochemical enzymatic biosensors for urea detection. 10,11 As shown in Eq. 1, the urea is hydrolyzed by urease, resulting in ammonium and, bicarbonate ions.…”