Application of a Screen-Printed Carbon Electrode Modified with Printex 6L and Deep Eutectic Solvent for Detection and Quantification of 17β-Estradiol

This work proposes the development of a screen-printed electrode (SPE) based on graphite ink as carbonaceous material and modified with a mixture of Printex 6L carbon and deep eutectic solvent (DES) (SPE-P6LCDES), used for detection and quantification of 17β-estradiol (E2) in mineral water, synthetic urine, and artificial saliva samples. The characterization of all electrodes was evaluated by Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) and Electrochemical Impedance Spectroscopy (EIS). Electrochemical measurements were performed in a system composed of a single compartment cell (100.0 mL), containing a reference electrode (Ag/AgCl/KClsat), Pt wire as a counter electrode and SPE as a working electrode. Electrochemical studies of E2 were performed in 0.1 mol L-1 phosphate buffer solution (PBS) at pH 7.0 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These studies evaluate the electroactivity of SPE-P6LCDES for E2, showing oxidative signals close to +0.98 V. The linear ranges of E2 concentrations studied were 0.00732 – 0.417 μmol L -1 for unmodified SPE and 0.00090 – 0.21 μmol L-1 for the SPE-P6LCDES, presenting limit of detection (LOD) of 0.177 μmol L-1 and 0.0065 μmol L -1, respectively. The use of DES + Printex 6L carbon as a modifier in the unmodified SPE allowed for strong intramolecular interactions between DES and the E2 molecule, which increased the intensity of the current responses because it is a sensor with greater sensibility, sensitivity, and reproducibility. The results obtained from the E2 recovery study on real samples were between 92.15% and 102.10%. By the method validation study (UV-Vis spectroscopy), the studied E2 concentrations of 10 and 60 μmol L-1 demonstrated recovery of +99.16% (+ 1.4%) and +100.16% (+1.9%), respectively.