We assessed the effect of the matrix and the studied antioxidants on the results of determining antioxidant capacity by a potentiometric method. An approach is proposed on an example of a hexacyanoferrate redox system, which takes into account the impact of these factors on the establishment of an equilibrium potential in the system with reducing any result distortion. The procedure involves introducing a series of additions of the oxidized component of the redox system after its interaction with a test sample. The approach results in constructing a calibration graph against the background of the sample matrix after the completion of the reaction of the antioxidant with an oxidant with determining the value of the prelogarithmic coefficient under the experimental conditions. The procedure was tested in the determination of individual antioxidants and in the analysis of samples of complex composition (extracts of plant raw materials) using both the redox system and its oxidized component.