Voltametric instrument

A basic voltametric instrument consists of a cell, a potentiostat, and a recorder. Chemical reactions are caused by applying a potential to an electrode in a cell. The current, which flows under the experimental conditions, is monitored with the recorder. The cell generally consists of three electrodes placed in seawater (1) the working electrode, usually a hanging drop of Hg or a Hg-plated graphite or glassy-carbon surface (2) the reference electrode, made of either calomel or Ag wire anodized to form AgCl and (3) a counterelectrode made of pure Pt wire. 

The approved variations [14] in the Karl Fischer method include volumetric titration methods to either a visual (excess iodine or addition of an indicator) or volta-metric endpoint detection method. The visual or voltametric endpoint methods usually require 30-40 mg of sample for analysis for freeze-dried biological products containing from 1.0% to 3.0% residual moisture. Coulometric Karl Fischer instruments generate the iodine from potassium iodide for water titration at the electrodes. Only 10-20 mg of freeze-dried sample is required for accurate analysis. 

In a survey of San Diego Bay waters we used the computer-controlled instrument in conjunction with the Orion Cu(II) ISE to travel in and out of waters that were relatively high in Cu concentration (4). The potentiomet-ric and voltametric data correlated very well. These data suggest that the combined use of the ASV instrument and the ISE may provide a way of obtaining quantified gradients of Cu activity in seawater. 

In a paper by Wasterlain et al. (2011) a new instrument developed in-lab is proposed to satisfy the requirements of electrochemical impedance studies to be led on large fuel cell plants made of numerous individual cells. Moreover, new voltammetry protocols dedicated to PEMFC stack analysis are described. They enable, for example, the study of membrane permeability and loss of platinum activity inside complete PEMFC assemblies. In the first part, a new electrochemical impedance spectrometer that makes testing large FC stacks possible has been presented. To validate this acquisition system and to demonstrate some of its capabilities, some experiments were conducted on a 20-cell PEMFC stack. In the second part, voltanunetry experiments were conducted on short FC stacks with a commercial potentiostat. The fuel crossover phenomenon in a three-cell PEMFC stack was analyzed using the linear sweep voltametric (LSV) method. The crossover rates were determined for each individual cell inside the complete assembly and for the entire stack as well. 

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See also in sourсe #XX -- [ ]

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