OTIMIZAÇÃO DE UMA METODOLOGIA ELETROANALÍTICA PARA DETERMINAR METILTESTOSTERONA EM AMOSTRAS AMBIENTAIS

Abstract

This work describes the development of an electroanalytical methodology for determining the hormone 17α-methyltestosterone in environmental samples, using the electrode hanging mercury drop (HMDE). Initially, studies were performed by cyclic voltammetry, which showed that 17α-methyltestosterone, has only a reduction peak at -1.35 V vs. Ag/AgCl,(in KCl 3.0 mol Lˉ¹), with features irreversible process and controlled by adsorption of species on the electrode surface. Parameters such as supporting electrolyte, hydrogen ion concentration of the medium, as well as, the parameters of the technique of square wave voltammetry (SWV) and frequency of application of potential pulses (ƒ), amplitude of pulses of potential (a) and scan increment (∆Es) were evaluated. Established the best conditions, working curves by the method of standard addition of 17α-methyltestosterone were obtained and the limits of detection (LOD) and quantification (LOQ) values were 3.07 μg Lˉ¹ and 10.78 μg Lˉ¹, respectively. The optimized methodology for the 17α-methyltestosterone was applied in purified water and natural to evaluate the presence of 17α-methyltestosterone in these matrices. The recovery curves obtained by standard addition technique, it was possible to determine amounts of 17α-methyltestosterone added in spiked samples. The recovering in purified water were 100.38%, and natural waters from 108.79% to 115.0%. The effects of matrices Interference were observed in natural water and with dilution of sample this effect was eliminated, allowing good recoveries at the level of trace analysis. The compound was quantified in samples of fish ponds in amounts up to 206.9 mg Lˉ¹. The study showed repeatability coefficient of variation (CV) of 2.85% and reproducibility CV of 14.91%, adequate in analysis of traces.