VALIDAÇÃO DE METODOLOGIA ANALÍTICA PARA DETERMINAÇÃO DE CARBONATO DE LODENAFILA POR VOLTAMETRIA

Abstract

This work describes the development and validation of a methodology for the quantification of lodenafil carbonate (LC) in pure form and pharmaceutical formulations. It was used the technique of square-wave cathodic adsorptive stripping voltammetry (SWCASV), employing the hanging mercury drop electrode (HMDE). Cyclic voltametry technique was employed in studies of the electrochemical behavior of the analyte, which demonstrated that the drug reduction process occurs irreversibly. The experimental conditions of analysis were optimized, such as the support electrolyte, pH and the parameters of the square wave voltammetry. The methodology was validated through studies of linearity, accuracy, precision, limit of quantification and limit of detection. The method was linear in the range from 0.150 μmol L-1 to 1.05 μmol L-1. The calculated quantification and detection limits were 13.8 nmol L-1 and 4.55 nmol L-1, respectively. In the precision studies, the values of relative standard deviation for the repeatability and the intermediate precision were calculated, being equal to 2.9% and 5.8%, respectively. The accuracy was evaluated by addition and recovery studies as well as by comparison with the spectrophotometric method in the ultraviolet region (UV). The data obtained in the addition and recovery studies were within the range considered adequate. The comparison of the methods was performed by means of a t-test that showed no significant difference between the two techniques. The electrochemical reduction of LC was also studied by controlled potential electrolysis using a mercury pool electrode in 0.1 mol L-1 H2SO4 solution with potential kept constant at -1.2 V vs Ag/AgCl. The products were characterized by infrared absorption spectroscopy, and from chemical-quantum calculations it was possible to propose a possible mechanism of reduction of the drug.