Carbon supported cobalt and nickel based nanomaterials for direct uric acid determination

Novel Co-Ni based catalysts on activated carbon support were prepared using NaBH₄ as a reducing agent in aqueous conditions and examined with respect to direct amperometric uric acid detection. The surface morphology and composition of the synthesised materials were examined using transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Cyclic voltammetry (CV) was employed in order to confirm the typical metallic electrochemical response of the Co, Ni and Co-Ni based materials. The combination of metal hydroxides/oxides and nanoparticles in the carbon supported Co-Ni based materials were found to play a key role in uric acid determination. Upon surface confinement of the Co₁Ni₁/C material, uric acid sensitivity 248.2 μA mM^-1 cm^-2 and limit of detection 0.08 μM at E_app=+0.4 V vs. Ag/AgCl was found by hydrodynamic amperometry over the range 0-250 μM (r²=0.9992). The sensor provided linear and reproducible behaviour over a wide range (25-575 μM) of uric acid. The composite materials showed excellent selectivity with respect to commonly found interferences with no response even at 10-fold concentration of urea, glucose and oxalate, and minimal influence of ascorbic acid (2 fold concentration). Overall, these materials are excellent candidates for direct uric acid detection in a stable, sensitive and very specific fashion over relevant physiological ranges, eliminating the pH, temperature sensitivity and lifetime issues associated with enzyme based systems. The materials are very promising for a range of applications including wound care/management and as non-enzymatic disposable uric acid test strips.