Determination of Ni with Electrodes Modified with Mordant Violet 5

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Abstract
The utility of electrodes modified with the dye Mordant Violet 5 (MV-5) for the determination of Ni is demonstrated. The method is based on the coordination of Ni from solution by an immobilized layer (via ion exchange) of the dye. Upon coordination the redox response of the dye is shifted in the negative direction by about 250 mV (from −0.74 to −0.97 V). The height of this peak is used as the analytical signal which is related to the concentration of Ni in solution. Linear calibration curves were obtained for Ni concentrations ranging from about 10−4 to 2×10−3M. Although this reflects only moderate sensitivity, a basic concept is established; this method allows for the determination of the metal via the redox response of the dye. Thus, with appropriate choice of reagents, metal ions difficult to determine by direct reduction can be determined by this method. The use of other reagents may result in enhanced sensitivity.