We are seeking for a surface modification which would not influence the electrochemical properties of different sensors used in the future. If a given modification deteriorates the catalyst, influences the mechanism or changes the environment of the reaction by e.g. local change of pH it should be discarded from future studies as it could lead to unexpected behavior of sensors and biosensors which we are planning to use. The influence of the protective layer on the catalyst was evaluated through observation of the shape of voltammograms and position of syringaldazine oxidation and reduction peaks depending on the pH.