Desenvolvimento de um método eletroanalítico para a determinação de sibutramina em amostras biológicas e forenses utilizando folha de grafite como eletrodo de trabalho

Abstract

The detection of sibutramine in different matrices is of significant importance due to its irregular use in dietary supplements and illicit weight-loss products, posing risks to public health and implications for forensic and antidoping analyses. In this context, electrochemical methods stand out as attractive alternatives to conventional techniques, offering low cost, rapid analysis, high sensitivity, and potential for in situ applications. This study aimed to develop an electroanalytical method for the determination of sibutramine (SIB) using a graphite sheet as the working electrode. Different surface modification strategies were evaluated, and electrochemical treatment was selected due to its superior analytical performance. The treated electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), demonstrating an increase in electroactive area and improved charge transfer kinetics. The electrochemical behavior of SIB was investigated, indicating a predominantly adsorption-controlled oxidation process. Differential pulse voltammetry (DPV) and square wave voltammetry (SWV) were evaluated, with SWV selected due to its higher analytical sensitivity. After optimization, two linear response ranges were obtained: 0.1–5.0 μmol L⁻¹ (R² = 0.993) and 7.5–45.0 μmol L⁻¹ (R² = 0.994). The limits of detection (LOD) were 0.01 μmol L⁻¹ for the first range and 1.89 μmol L⁻¹ for the second, while the limits of quantification (LOQ) were 0.03 μmol L⁻¹ and 6.32 μmol L⁻¹, respectively. The developed method was successfully applied to the determination of SIB in synthetic urine, multivitamin samples, and seized materials, showing satisfactory recovery results. Validation was performed through comparison with an HPLC-UV/Vis reference method, demonstrating good agreement between the results. The findings indicate that the electrochemically treated graphite sheet electrode is a promising, low-cost, and easy-to-prepare alternative for the determination of SIB in different matrices, with potential applications in forensic analysis, sanitary control, and antidoping.