Desenvolvimento de eletrodos de pasta de carbono a base de polidimetilsiloxano aplicados para a quantificação de propranolol em formulações farmacêuticas

Abstract

An electroanalytical method for the determination of propranolol in pharmaceutical formulations is described. Initially, poly (dimethylsiloxane-co-alkylmethylsiloxane functionalized silica-modified carbon paste electrodes - CPE/Si (PDAS) were used for drug detection by anodic stripping voltammetry using the differential pulse technique. For analytical comparisons, a non-functionalized silica modified carbon paste electrode was prepared - CPE / Si-Gel. Si(PDAS) and Si-Gel modified carbon paste electrodes did not allow the development of an electroanalytical method for determination of propranolol, since it was not possible to obtain reproducible linear range. Alternatively, a carbon paste electrode prepared with 80% carbon powder and 20% polydimethylsiloxane (PDMS) - CPE/PDMS was used in the determination of propranolol and for comparison another electrode was prepared under the same conditions using Nujol® as binder - CPE/NUJOL. The analytical curves constructed for propranolol using both electrodes were linear in the range of 10 to 60 μmol L-1, with R2 = 0.997 for CPE/PDMS and R2 = 0.981 for CPE/NUJOL. The limits of detection and quantification obtained for the CPE/PDMS were 3 and 10 μmol L-1 and for the CPE/NUJOL were 8 and 27 μmol L-1, respectively. From the images obtained by scanning electron microscopy was verified that the paste prepared with PDMS showed a less rough morphology, which could explain the lower residual currents and, consequently, the better detectability of this electrode when compared to the paste prepared with Nujol®. The proposed method using the CPE/PDMS was applied in the determination of propranolol in 4 different drug samples, which were also analyzed by spectrophotometry in the UV-vis region. The amounts of PROP found in the samples of pharmaceutical formulations employing both methods were in agreement with the content reported by the manufacturer. Moreover, no evidence of statistical differences was found between the PROP content obtained by the proposed voltammetric method and the UVvis spectrophotometric method, since the calculated F and t values were lower than the critical values. Thus, CPE/PDMS proved to be efficient to determine propranolol in samples of pharmaceutical formulations.