Influence of the physical properties and handling of silica gel modified carbon paste electrodes on the phase transfer of solved Cu(II) ions [An article from: Analytica Chimica Acta]

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Description:
Carbon paste electrodes (CPE) modified with natural minerals might be utilised to mimic adsorption/desorption reactions at natural interfaces. As a step towards this aim, several properties and application conditions of CPEs, modified with silica gel, were tested for their influence on phase transfer reactions of solved Cu(II)-tetrammine complex ions. The peak current recorded during the anodic stripping of adsorbed Cu(II) species increased with increasing diameter of the circular electrode surface. A silica gel content of 29 mass percent yielded the highest peak current at otherwise constant exposition conditions. A substitution of graphite by glassy carbon did not enhance the electrode sensitivity. The peak current increased with increasing exposition time (up to 20min) and with decreasing size of the modifier particles. Typically between 12% and 22% of the solved Cu ions were adsorbed onto the electrode surface and between 15% and 20% of this Cu fraction was subsequently removed by stripping and electrode regeneration. Despite the incomplete electrode regeneration the mass transfer ratios of the Cu(II) species were relatively constant during several application cycles.