Study of the interaction between caffeine and graphenic materials employing computational analysis and electrochemistry

Caffeine (CAF), present in various pharmaceutical formulations and food supplements, is one of the most consumed substances worldwide. Therefore, it is necessary to develop ways to monitor the presence and quantity of this compound in the environment and pharmaceutical industries. Thus, the present study reports the construction of a sensor that employs a reduced graphene oxide–modified glassy carbon electrode (rGO/GCE) to detect caffeine molecules in a 0.5 mol L−1 H2SO4 solution. Combining the density functional theory (DFT) simulations and electrochemical tests enhances our knowledge of the caffeine oxidation process between the CAF and rGO surfaces. Furthermore, a 26−2 fractional experimental design allowed the evaluation of the optimal conditions for preparing the rGO-modified electrode. Differential pulse voltammetry was optimized using a face-centered composite design with a step potential of 5 mV and a modulation amplitude of 50 mV. After this, employing the optimized method to quantify CAF, the value of the limit of detection obtained was 0.53 μmol L−1 in a 0.5 mol L−1 H2SO4 using the rGO/GCE sensor. The proposed methodology was able to quantify pharmaceutical samples with different compositions, with recoveries between 88.7 and 95.7