Biochemical compounds play important roles in various biological processes and their determination in physiological fluids are necessary in the diagnosis and treatment of diseases. In this work a new biosensor is introduced based on stainless steel (SS) for simultaneous determination of levodopa (LD) and uric acid (UA).In order to prepare the modified electrode for this work, SS is rubbed and anodized to fabricate nanoporous stainless steel (). Then, electrodeposition of Cu onto the nanopores of the electrode was done by applying multiple step potential method (Cu/). Finally, for galvanic replacement the electrode is immersed into the solution contain 3 mM of gold and palladium by atomic ratio of 9:1 (Au-Pd/). Morphological aspects, structure, properties and electroanalytical behavior of Au-Pd/ electrode were studied using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Also differential pulse voltammetry (DPV) was used for optimization of parameters such as pH, electrode preparation and DPV parameters and the simultaneous determination of LD and UA. According to results, the surface of Au-Pd/ electrode contains a layer of Au and Pd nanoparticles with 75 nm average diameter and the mass amounts of Au and Pd are 15.08% and 0.96% respectively. LD and UA were successfully determined by Au-Pd/ electrode; where calibration curve for LD was in two concentration ranges of 5.0-10.0 and 10.0-55.0 ?M and for UA was in the range of 100-1200 ?M. The detection limit for LD and UA were 0.2 and 15 ?M, respectively, and obtained oxidation peak separation of them was at 220 mV. The result illustrates the modified electrode can successfully applied for determination of LD and UA in urine, blood serum and levodopa C-Forte tablet.
