Aplicação de um sensor eletroquímico impresso e modificado com um solvente eutético para detecção de 17Β-estradiol e progesterona

Abstract

Electrochemical sensors have been used to control the dosage of emerging contaminants, mainly in endocrine compounds, including 17β-estradiol (E2) and Progesterone (P4). Thus, the present work proposes the development of a graphite-based screen-printed paper electrode (SPE) doped with a mixture of Printex 6L carbon (SPE-P6LC) and deep eutectic solvent (DES) (SPE-P6LCDES), used for detection and quantification of E2 and P4 in mineral water, synthetic urine and artificial saliva samples. The physical characterization of the electrodes was evaluated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Optical Microscopy (OM). The electrochemical characterization of the electrodes was performed using the techniques of Cyclic Voltammetry (VC) and Electrochemical Impedance Spectroscopy (EIE). The electrochemical measurements were performed in a system composed of a single compartment cell (100 mL), containing a reference electrode (Ag/AgCl/KClsat.), Pt wire as counter electrode and SPE as working electrode. Studies of the variation of graphite ink layers, variation of the proportion of graphite ink, as well as the cyclic repeatability and reproducibility of the electrodes were carried out by VC in 0.5 mol L-1 potassium chloride (KCl) support electrolyte containing 1 mmol L-1 of redox pair Fe(CN)6 3-/4- . From these studies, it can be verified that the adherence of 2 layers of graphite ink in the proportion the graphite:varnish 50%/50% (w/v) had better electrochemical responses from the values calculated by the reversibility criteria, corroborating the results of reproducibility and repeatability of the electrodes. The electrochemical stability of SPE was also evaluated by the chronoamperometry technique in 0.5 mol L-1 KCl containing 1 mmol L-1 Fe(CN)6 3-/4- , which presented oscillations of ~2.0% during the 8 hours period. Subsequently, the electroactivity of E2 and P4 were evaluated by differential pulse voltammetry (DPV) in 0.1 mol L-1 phosphate buffer solution (PBS) at pH 7.0 and 4.0, respectively. With these studies, oxidative signals of E2 and P4 were observed close to +0.98V and 0.54 V, respectively. The linear ranges of E2 concentrations studied were 0.00732 – 0.417 μmol L-1 (LD= 0.177 μmol L-1 ) for non-doped SPE and 0.00090 – 0.21 μmol L -1 (LD= 0.0065 μmol L-1 ) for the SPE-P6LCDES. For the P4 detection study, the linear concentrations ranges were 0.0090 – 0.812 μmol L -1 (LD= 0.00582 μmol L-1 ) and 0.00080 – 0.050 μmol L -1 (LD= 0.00075 μmol L-1 ) for the non-doped SPE and SPE-P6LCDES, respectively. The use of DES + Printex 6L carbon as a dopant of the SPE, allowed strong interactions intramolecular with the analyte molecules, increasing the intensity of the current responses, being a sensor with greater sensitivity, selectivity and reproducibility. E2 and P4 recovery studies were performed in the SPE-P6LCDES in mineral water, synthetic urine and artificial saliva samples, obtaining recoveries between 92.15% - 110.01%. By method validation study (UV-Vis Spectroscopy), the E2 and P4 concentrations studies (10 and 60 μmol L-1 ) demonstrated recovery results between +99.16% (+1.4%) and +100.16% (+1.9%).