Standard addition method with cumulative spikes: uric acid determination in human serum by voltammetry with optimized uncertainty

Accreditation and Quality Assurance - This work presents a low-cost, simple and adequately reliable voltammetric alternative to the determination of uric acid (UA) in human serum by the enzymatic...     

An electrochemical sensor for dipyrone determination based on nickel-salen film modified electrode

An amperometric dipyrone sensor based on a polymeric nickel-salen (salen = N,N´-ethylenebis(salicydeneiminato)) film coated platinum electrode was developed. The sensor was constructed by electropolymerization of nickel-salen complex at a platinum electrode in acetonitrile/tetrabuthylamonium perchlorate by cyclic voltammetry. After cycling the modified electrode in a 0.50 mol L^-1 KCl solution, the estimated surface concentration was found to be equal to 1.29 x 10^-9 mol cm^-2. This is a typical behavior of an electrode surface immobilized with a redox couple that can usually be considered as a reversible single-electron reduction/oxidation of the nickel(II)/nickel(III) couple. A plot of the anodic current versus the dipyrone concentration for chronoamperometry (potential fixed = +0.50 V) at the sensor was linear in the 4.7 x 10^-6 to 1.1 x 10^-4 mol L^-1 concentration range and the concentration limit was 1.2 x 10^-6 mol L^-1. The proposed electrode is useful for the quality control and routine analysis of dipyrone in pharmaceutical formulations.