Development of a non-enzymatic urea sensor based on a Ni/Au electrode

Measurement of urea concentration in urine is a very important parameter for determining the state of kidney health. With this aim, a non-enzymatic urea sensor comprising Ni metal deposited on an Au electrode has been developed. Ni was first deposited on an Au electrode by varying the potential and time, and then the deposited Ni was activated in KOH to generate NiOOH, which can oxidize urea to CO₂, N₂ and H₂ to allow it to be detected electrochemically. The results show that the Ni/Au electrode can be used to detect urea with a limit of detection (LOD) value of 3.35 - 10^-2 mM, a sensitivity of 52.20 mMμA^-1cm^-2 and a linearity of r² = 0.997 at a deposition potential of -0.45 V vs. Ag/AgCl after a deposition time of 180 seconds. The Ni/Au electrode has good repeatability and reproducibility (%RSD value) of 0.12% (n = 12) and shows good stability with a %RSD value of 1.60% after 9 days. The Ni/Au electrode performance is not disturbed by the presence of any interfering compounds, such as ascorbic acid, glucose, NaCl, and KCl. The Ni/Au electrode can be used to measure urea levels in urine samples, detecting concentrations of as high as 9.615 mM.