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New Strategy in Electroanalysis: Elimination Voltammetry on Polymer Pencil Graphite Electrodes

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TRNKOVÁ Libuše TŘÍSKOVÁ Iveta KEJÍK Martin MORAVEC Zdeněk HRBÁČ Jan

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Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
Popis Analytical electrochemistry has undergone many important developments conditioned by better understanding of electrode processes and improvements in instrumentation, which have allowed faster measurements to be made under better-controlled conditions [1]. In spite of its fast and perspective development some drawbacks, such as imperfect knowledge of the electrode surface and low reading value of registered signals, persist. This contribution presents interesting solutions not only for addressing major shortcomings of linear sweep and cyclic voltammetry (low sensitivity, high proportion of capacitive current component, and skewing of overlapping signals) in the form of the elimination voltammetry [2-4], but also addresses graphite electrode material in the form pencil leads [5]. To understand interactions between analytes and electrode surface groups or to know the origin of additional electroanalytical signals the polymer pencil graphite electrodes (pPeGE) were investigated by modern non/electrochemical methods (Raman, energy-dispersive X-ray and infrared spectroscopies) which indicate low degree of oxygenation, unexpectedly high content of sp3 carbon and the presence of substoichiometric amount of silicon oxide (SiO). It was found that pPeGEs exhibit higher electron transfer rates and at the same time lower double layer capacitance values in comparison with the common carbon electrodes (glassy carbon, highly oriented pyrolytic graphite). Based on both spectroscopic and voltammetric results new graphite electrodes with nanostructured silica materials were prepared. To obtain more information from voltammetric experiments the elimination voltammetry with linear scan (EVLS) was applied. Based on the different dependences of the particular currents of which the total voltammetric current is composed (i.e. diffusion, charging, kinetics, etc.) on scan rate, the EVLS is capable of eliminating or conserving some chosen current components. The voltammetric results are improved in both aspects, i.e., the sensitivity increase and the selectivity improvement. The advantages of EVLS consist in the ability: (a) to detect the processes hidden in the predominant current, such as the discharge of the supporting electrolyte, (b) to increase the current sensitivity by at least one order of magnitude, (c) to determine the charge transfer coefficient, and (d) to detect the chemical reaction preceding the electron transfer. Thus, the EVLS in combination with modified pencil graphite electrodes offers a new tool contributing to better understanding of basic electrochemical processes on the electrode surface, and at the same time it is capable of markedly improving the sensitivity of voltammetric assays.
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