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SnO2 electrodes in the form of thin, highly doped films on glass were exposed to aqueous RuCl3 solutions and examined electrochemically and by x-ray photoelectron spectroscopy (XPES). For both native SnO2 and SnO2 silanized with an alkylamine silane, the Ru is strongly chemisorbed and yields a broad chemically reversible surface wave near 0V and an irreversible oxidation wave near +0.85V. These are interpreted as Ru(II~-.IIl) and Ru(IlI--> IV) processes, respectively. XPES sputtering experiments reveal the existence oK suDsurmce Ru at depths similar to observed O/Sn nonstoichiometry.

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 to ~x~O -~M . Although this reflects only moderate sensitivity, a basic concept is established; this method allows for the determination of 1521 Copyright 0 1987 by Marcel Dekker, Inc. Downloaded by [McMaster University] at 15:12 08 February 2015 1522 MC CRACKEN, WIER, AND ABRUNA the metal via the redox response of the e. 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. INTRODUCTION: