Electrochemical Determination of Dipyrone Using a Cold-Plasma-Treated Graphite Sheet Electrode

The development of fast, reliable, and cost-effective techniques for pharmaceutical compound analysis is an issue of paramount importance to the pharmaceutical industry, environmental sciences, and many other applications. In this work, a low-cost graphite sheet electrode (GSE) was used as a disposable working electrode. To this purpose, the GSE surface was subjected to a cold plasma discharge using a mixture of argon and O₂. The sensor was applied to dipyrone (DIP) quantification. Initially, the influence of pH on the electrochemical response of DIP on the pyrolytic graphite sheet (PGS) electrodes was evaluated using a 0.12 mol L^-1 Britton-Robinson buffer solution at pH values ranging from 2.0 to 12.0. The solution adjusted to pH 4.0 was selected as the supporting electrolyte for the experiments since a larger current intensity was obtained at this medium. The mass transport of DIP toward the PGS surface was investigated by cyclic voltammetry, evidencing a diffusion-controlled process. DIP was initially quantified by square wave voltammetry (SWV) with a linear range of about 2.5-200 μmol L^-1 and a calculated limit of detection of about 0.31 μmol L^-1. Finally, SWV was used to enable DIP detection in synthetic urine solutions, demonstrating its applicability as a sensor tool in real analysis.