Desenvolvimento de sensores eletroquímicos baseados em nanomateriais de carbono para detecção de diquat em amostras ambientais e tadalafila em amostras farmacêuticas

Abstract

In this work two electrochemical sensors were proposed based on carbon nanomaterials for detection of diquat and tadalafil. For the first was proposed a surface modification of glassy carbon electrode with manioc starch and nanodiamonds dispersion. The other sensor was based on a film of vertically aligned carbon nanotubes with a copper plate like substrate. The glassy carbon electrode modified with nanodiamonds and manioc starch film was characterized electrochemical and morphological characteristics through techniques such as cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and x-ray diffraction to understand the electrochemical behavior of the film. Many techniques were analyzed regarding the behavior and quantification of diquat, however, the technique that presented the highest peak current was the square wave voltammetry. After the choice of chemical and electrochemical parameters, was constructed an analytical curve with a linear range of 5.0×10−7 to 4.6×10−5 mol L −1. The limit of detection was 1.1×10−7 mol L− 1. Water samples fortified with diquat were analyzed. In comparison to the works, the glassy carbon electrode modified with nanodiamonds and manioc starch film has a good linear range and a low limit of detection. For the second electrode was chosen for morphological characterization through images obtained by scanning electron microscopy, as well as transmission; in addition to electrochemical characterizations acquired by cyclic voltammetry from the potassium ferri/ferro-cyanide like redox probe. In order to study the electrochemistry of tadalafil were analyzed some voltammetric techniques like cyclic voltammetry, linear sweep voltammetry, differential pulse voltammetry and square wave voltammetry, especially the linear sweep voltammetry in which the device reached the highest anodic peak current. Optimizing the parameters, the analytical determination of tadalafil comprised a linear concentration range of 0.85 to 8.9×10−6 mol L−1 where the limit of detection was 7.8×10−8 mol L−1. The samples selected for validation of the device were drugs obtained from pharmacies in the city of Araras being a generic and a manipulated drug.