Eletrodos voltamétricos e amperométricos para a determinação de espécies de interesse farmacêutico

Abstract

The development of modified electrodes by insoluble metal hexacyanoferrates have attracted wide spread attention due to their interesting chemical and electrochemical characteristics. In the first developed work, 20% (m/m) of copper(II) hexacianoferrate was incorporated to a carbon paste for the voltammetric determination of dipyrone. The analytical curve showed a linear response in the concentration range of 9.9 x 10-6 to 2.4 x 10-4 mol L-1 with a detection limit of 8.1 x 10-6 mol L-1 in acetate buffer solution at pH 7.3. In a second work, an anionic exchange resin modified with hexacianoferrate(III) ions was used as modifier material in an MCPE that later was applied in the amperometric determination of paracetamol. The analytical curve was linear in the paracetamol concentration range of 2.0 x 10-5 and 6.5 x 10-4 mol L-1 with a detection limit of 1.6 x 10-5 mol L-1. The use of vanadium complexes has been also intensified in the last years, mainly for its importance in diverse biochemist processes in the human body. In this work, two other methods had been proposed employing an EPCM with VO-Salen complex for the voltammetric determination of dipyrone and ranitidine in pharmaceutical products. The analytical curves for dipyrone and ranitidine were linear in the concentration ranges of 9.0 x 10-6 to 2.8 x 10-4 mol L-1 and 9.9 x 10-5 to 1.0 x 10-3 mol L-1, respectively, with a detection limit of 7.2 x 10-6 mol L-1 for dipyrone and 6.6 x 10-5 mol L-1 for ranitidine. Finally, the use of carbon paste electrodes, modified or not, coupled to the FIA system with amperometric detection has been also widely explored due to be an extremely versatile alternative. In this work, a procedure for the captopril quantification in pharmaceutical formulations was developed using an amperometric flow cell connected to the FIA system. The method was based on the reaction of the captopril oxidation, under action of an applied electric potential. Parameters such as pH and support electrolyte, and the FIA system parameters had been evaluated in order to get the best results. The analytical curve was linear in the captopril concentration range from 2.0 x 10-4 to 7.5 x 10-3 mol L-1, with a detection limit of 9.6 x 10-5 mol L-1 and a sampling frequency of 42 h-1.