Emma Muñoz

Analysis and speciation of arsenic by stripping potentiometry: a review

This paper provides a review that summarizes several examples of the literature from 1980 to 2003, to illustrate the applications of stripping potentiometry for the determination and speciation of arsenic in several samples. A discussion on the main advantages of stripping potentiometry in comparison with other electrochemical methods employed for arsenic determination is presented. Special attention is devoted to stripping modes (constant current or chemical stripping) and to issues related to the choice of working electrodes and supporting electrolyte. This approach has been also applied at arsenic determination in flow systems. A section is dedicated to speciation of arsenic and total arsenic determination and other to analytical characteristic of method and their interferences. An extensive compilation, organize by experimental and analytical parameters and real sample studied is presented.

Electrochemical Behavior of Menadione on Glassy Carbon Rotating Disk Electrode (RDE)

The 2-methyl-1,4-naphthoquinone electrochemical behavior on glassy carbon rotating disk electrode has been the focus of this study. In order to obtain the best results, the optimal conditions for this voltammetric study have been determined, by performing a chemometric analysis of the data. The influence of five factors on the diffusion current has been studied, finding that the greatest effect is due to three of them. The optimum values for all of these parameters were: pH 7, v (potential sweep rate)=87.1 mV/s, Cmet (methanol concentration)=4.14 %(v/v), teq (equilibrium time)=2.5 min, and tdea (purge time)=2 min. These data were used to determine the mass transfer parameters: diffusion coefficient (D=(1.4±0.3)×10–4 cm2/s) and diffusion layer thickness (δ=(6.6±0.5)×10–3 cm), the kinetic parameters: charge transfer constant (K0=2.91×10–6 cm/s) and charge transfer coefficient (α=0.248), and the standard potential (E0=0.083±0.011 V).

Fast Linear Scan Stripping Voltammetry of Copper Using a Glassy Carbon Rotating Disk Electrode

Fast scan stripping voltammetry is applied to copper determination, using a rotating glassy carbon electrode as working electrode. Optimal conditions are determined by an experimental design where the current peak is chosen as response factor. The effects of different parameters (deposition potential, deposition time, electrode rotation rate and potential sweep) and their interdependence is optimized. A value of 2.8×10–10 M is obtained for the detection limit, with a relative standard deviation of 0.16 in four replicated assays. The method is applied to the determination of copper in tap water and in some chemicals (HClO4, HNO3, etc.).