Effect of Direct Current and Periodic Polarization on Differential Electrolytic Potentiometric Signal Produced By Carbon Nanotube Electrode

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In differential electrolytic potentiometry (DEP), a pair of identical indicator electrodes is polarized using either a very small, heavily stabilized direct current (DC) or a periodic square waveform (SW) of constant amplitude. The square wave can be biased or bias-free. In this study, carbon nanotube-modified silver electrodes, CNT-Ag, were used as the DEP indicating system with all types of polarization. This was done to investigate how the polarization mode affects the signal intensity, shape, position, and amplification. The method was applied to analyze various analytes including ascorbic acid, Fluoroquinolone, cyanide, and chloride using normal titrimetric and sequential injection analysis (SIA) methods. Many of the findings showed that raising the polarizing direct current density (µA/cm2) boosts the DEP peak until reaching a certain point, after which the peaks begin to widen and the position of the peak center shifts. Similar changes were observed when increasing the percentage bias of the square waveform used to polarize the CNT-Ag indicator electrodes. The free-biased square waveform led to the least improvement in peak intensity. As the percentage bias increased, the peak intensity improved up to a certain level. However, beyond that point, all peaks began to broaden without further enhancement in intensity. In all cases, periodic polarization of electrodes produced a much greater enhancement in peak intensities compared to direct current polarization. With square-wave polarization, the ongoing reversal of polarity prevents the accumulation of films on the electrodes, speeds up the response, and substantially reduces electrode fouling and deactivation.Furthermore, aside from the advantages of the periodic polarization, the CNT-Ag electrode, fabricated through chemical vapor deposition with aligned and well-structured CNTs, contributes to boosting the DEP peak intensity by promoting heterogeneous electron transfer. This process facilitates fast equilibrium, leading to precise and reproducible results. Figure 1