This graduate thesis presents the results of research on the behavior of caffeic acid on variously modified glassy carbon electrodes. Electrochemical tests were performed in three different buffer solutions (acetate, wine model solution, Britton-Robinson buffer) at different pH values (2,6-6,6 in Britton-Robinson buffer). A significant dependence of the electrochemical behavior of caffeic acid on the modified electrodes was observed depending on the buffer in which the measurements were performed. Britton-Robinson buffer proved to be the most suitable buffer, while significant kinetic limitations were noted in acetate buffer. The kinetic constraints related to electron transfer across the heterogeneous phase boundary were investigated over a wide range of scan rates. A complex control mechanism of the electrochemical behavior of quercetin on the prepared electrodes guided by cascade (sequential redox reactions) was determined. The effect of pH on the electrochemical behavior of quercetin was examined in the pH range of 3.6 to 6.6. . Increasing the pH value shifts the potential of current peaks, but also reduces the sensitivity. These phenomena are explained in the context of the proposed mechanisms of oxidation/reduction of quercetin. Significant effects of forced convection on the electrochemical response as well as measurement times and types of buffers that control the chemical stability of quercetin were observed. These studies indicated that the behavior of quercetin on electrodes modified with carbon nanomaterials is of a complex character and is not controlled by a single parameter, but by a combination of both diffusion and adsorption. As the most optimal system for determining quercetine, based on the analysis, electrodes modified with carbon nanotubes in Britton-Robinson buffer, at pH 3.6, but also electrodes modified with electrochemically reduced graphene in solutions of wine models and Britton-Robinson buffer with less sensitive and more stable in response. The results of this thesis, together with the results obtained with other polyphenols on the same electrodes can help to overcome interference, increase sensitivity and develop new methods for the determination of polyphenols in real samples.