Susana Palmero

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.

Development of a Novel Bidimensional Spectroelectrochemistry Cell Using Transfer Single-Walled Carbon Nanotubes Films as Optically Transparent Electrodes

A really easy method to transfer commercial single-walled carbon nanotubes (SWCNTs) to different substrates is proposed. In this paper, a homogeneous transference of SWCNTs films to nonconductor and transparent supports, such as polyethylene terephthalate, glass, and quartz, and to conductor supports, such as indium tin oxide, aluminum, highly ordered pyrolytic graphite, and glassy carbon, was achieved using a very fast, reproducible, and clean methodology. In order to test these transferences, SWCNTs films transferred on quartz were used as working optically UV-vis transparent electrodes due to their optimal electrical and optical properties. A new easy-to-use, homemade optical fiber based cell for bidimensional spectroelectrochemistry was developed, offering the possibility to measure in normal and parallel configuration. The cell was tested with ferrocenemethanol, a compound widely used in electrochemistry but scarcely studied by spectroelectrochemistry, covering the UV-vis spectral region.

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.).

Carbon nanostructured films modified by metal nanoparticles supported on filtering membranes for electroanalysis

A novel methodology to prepare sensors based on carbon nanostructures electrodes modified by metal nanoparticles is proposed. As a proof of concept, a novel bismuth nanoparticle/carbon nanofiber (Bi-NPs/CNF) electrode and a carbon nanotube (CNT)/gold nanoparticle (Au-NPs) have been developed. Bi-NPs/CNF films were prepared by 1) filtering a dispersion of CNFs on a polytetrafluorethylene (PTFE) filter, and 2) filtering a dispersion of Bi-NPs chemically synthesized through this CNF/PTFE film. Next the electrode is prepared by sticking the Bi-NPs/CNF/PTFE film on a PET substrate. In this work, Bi-NPs/CNF ratio was optimized using a Cd2+ solution as a probe sample. The Cd anodic stripping peak intensity, registered by differential pulse anodic stripping voltammetry (DPASV), is selected as target signal. The voltammograms registered for Cd stripping with this Bi-NPs/CNF/PTFE electrode showed well-defined and highly reproducible electrochemical. The optimized Bi-NPs/CNF electrode exhibits a Cd2+ detection limit of 53.57 ppb. To demonstrate the utility and versatility of this methodology, single walled carbon nanotubes (SWCNTs) and gold nanoparticles (Au-NPs) were selected to prepare a completely different electrode. Thus, the new Au-NPs/SWCNT/PTFE electrode was tested with a multiresponse technique. In this case, UV/Vis absorption spectroelectrochemistry experiments were carried out for studying dopamine, demonstrating the good performance of the Au-NPs/SWCNT electrode developed.