Adsorptive Stripping Voltammetry in Trace Metal Electroanalysis. Case Study: Dimethylglyoxime Complexes.

RAMIREZ, S.A.; GORDILLO GABRIEL J.

Electroanalytical Chemistry Research Developments

Nova Science Publishers

Lugar: New York; Año: 2007; p. 255 - 278

ABSTRACT In recent times, a great number of studies have been published focusing on the presence of metals in the environment with potential or proved toxicity. The recent quantification of heavy metals in urban atmospheric dust samples has demonstrated the presence of certain metals such as platinum and palladium, which originate in emissions from the vehicles’ catalytic converters. In order to obtain reliable information about metal content, which could be used to evaluate their bioavailability and bioaccumulation, it is still relevant to invest efforts in the development of specific methods for the quantification with suitable sensibility. The electrochemical techniques involving preconcentration of metal complexes, also known as adsorptive techniques, have shown to be extremely useful for the determination of heavy metals in the ppb and sub-ppb levels. In the case of the platinum group metals (PGM: Pt, Pd, Rh, Ru, Ir and Os), and also other transition metals like Co and Ni, dimethylglyoxime (H2DMG) has been successfully applied. In this work we study the electrochemical and adsorptive behaviour of Ni, Co, and Pd-dimethylglyoxime complexes by using voltammetric and capacitive measurements. Surface charge due to the reduction of the adsorbed molecules has been correlated with the differential capacity. On the basis of these results, we consider the possibility of the existence of different surface orientations of the adsorbed molecules. The analysis of the voltammetric response allows us to propose a reduction mechanism for the complexes. Even though the literature emphasizes the similarity in the electrochemical behavior of all three mentioned complexes, our results show important differences so much in the adsorption kinetics, the surface states and the electrochemical reduction. The present study can be used in the optimization of a technique for the simultaneous determination of these metals.