Electrodeposited nanoporous ruthenium oxide for simultaneous quantification of ascorbic acid and uric acid using chronoamperometry at two different potentials

Nanoporous ruthenium dioxide (RuO₂) was simply prepared by electrodeposition with potential cycling in RuCl₃ solution in the presence of reverse micelles of Triton X-100. The electrodeposited RuO₂ on Au substrate electrode showed high electroactivity for the oxidations of L-ascorbic acid (AA) and uric acid (UA), while AA oxidation started from a less positive potential compared to UA oxidation. Simultaneous quantitative analysis of AA and UA was successfully carried out via chronoamperometric measurements at two different applied potentials using RuO₂ deposited electrode. Due to the oxidation potential difference between AA and UA at RuO₂ electrode, only AA was oxidized at an applied potential of 0.20 V vs. SCE and both AA and UA were oxidized at 0.32 V vs. SCE. AA concentration was determined from the current measured at 0.20 V; and then UA concentration was estimated from the current measured at 0.32 V using the predetermined AA concentration. Electrodeposited nanoporous RuO₂ electrode exhibited current responses linearly proportional to AA and UA concentrations in a wide concentration range (0–1 mM) and fast response time (≤1 s). The current sensitivities were 342.8 ± 26.3 μA mM⁻¹ cm⁻² for AA at 0.20 V; 377.8 ± 18.4 μA mM⁻¹ cm⁻² for AA at 0.32 V; and 344.2 ± 11.6 μA mM⁻¹ cm⁻² for UA at 0.32 V. In addition, RuO₂ electrode showed a high selectivity over interferents such as 4-acetamidophenol (AP), dopamine (DA), and glucose. Reasonable stability and repeatability of RuO₂ electrode were also confirmed. Selective quantification of AA and UA in an arbitrary mixture and a human urine sample demonstrated that RuO₂ electrode has practical utility in real sample analysis with satisfactory results.