Solvent effects on the graphite surface targeting the construction of voltammetric sensors with potential applications in pharmaceutical area

In this paper the effect of different solvents (ethanol, acetone, dichloromethane and hexane) in the surface treatment of graphite for the construction of voltammetric sensors was evaluated. During voltammetric experiments of the graphite powder-based sensor treated with ethanol, it was possible to observe a significant increase in current signals for the redox process of the model analyte (acetaminophen), as well as an increase in the area density of this sensor compared to its unmodified electrode. Theoretical studies involving Density Functional Theory (DFT) and Quantum Theory of Atoms in Molecules (QTAIM) showed greater interaction and stability when graphite was treated with ethanol solvent. Moreover, the theoretical calculations indicated that treating the voltammetric sensor with ethanol offers improvements in the electrochemical response of the model analyte mainly due to a higher spin density, and a partially covalent interaction between solvent and graphite surface. Therefore, graphite powder-based sensors treated with ethanol were used for determination of acetaminophen in pharmaceutical samples and their results were in good agreement with those obtained by using spectrophotometric method recommended by Pharmacopoeia.