First sets of experiments were conducted on standard commercial glassy carbon electrodes 3 mm in diameter (Figure ). However, we have noted that in some cases such a big area resulted in uneven spreading of the layer, formation of cracks or adhesion problems in some of the tested materials. As the goal of this work was to find a suitable electrode modification strategy that would be used in electrode arrays in which the size of the electrode ranges from tents to hundreds of micrometres, we have decided to use other electrodes that could be easily cleaned, or bought/fabricated in large quantities and their surface would be made from some carbon material to allow for easy modification with syringaldazine. Commercial, multichannel screen printed carbon electrodes were our first choice, but after modification with syringaldazine additional peaks were visible on the voltammograms and the results were not reproducible(Figure .). The electrodes were tested in buffer solutions and solution of standard redox probes in which their response was as expected. We have tried to clean the electrodes through washing in organic solvents, or electrochemical cycling in solutions of bases or acids but it was still not possible to observe clean signal from syringaldazine. The problem was attributed to inherent impurities from the electroactive paint, which in some way interact with syringaldazine. Such impurities are common in SPE carbon inks, and can show up as additional peaks visible in background scans but are usually dwarfed by the signal of the analyte .