Stripping voltammetry silver electrodes

Other metals, such as copper, nickel, or silver, have been used as electrode materials in connection with specific applications, such as the detection of amino acids or carbohydrates in alkaline media (copper and nickel) and cyanide or sulfur compounds (silver). Unlike platinum or gold electrodes, these electrodes offer a stable response for carbohydrates at constant potentials, through the formation of high-valence oxyhydroxide species formed in situ on the surface and believed to act as redox mediators (40,41). Bismuth film electrodes (preplated or in situ plated ones) have been shown to be an attractive alternative to mercury films used for stripping voltammetry of trace metals (42,43). Alloy electrodes (e.g., platinum-ruthenium, nickel-titanium) are also being used for addressing adsorption or corrosion effects of one of their components. The bifunctional catalytic mechanism of alloy electrodes (such as Pt-Ru or Pt-Sn ones) has been particularly useful for fuel cell applications (44). 

The preconcentration of trace metals by electrodeposition is an integral part of anodic-stripping voltammetry. The method consists of the preelectrolysis of the stirred solution with a small mercury drop or solid electrode as the cathode (112-114). The metals, which are deposited and dissolve in the mercury, are then stripped from the amalgam after a suitable rest period by a reversal of the electrode potential. The resulting current-polarization curve is characteristic of the metal and its concentration. Concentrations as low as 10 M of metal ions require a preelectrolysis of about 60 min or longer. Other electrodes such as mercury films, platinum, gold, silver, and various forms of carbon have been used (77 ). 

Anodic stripping voltammetry was in use already in 1972 to determine Bi in plasma [120]. Bismuth is one of the elements most easily determined with this method. It can be deposited on electrodes at potentials at which most other elements ate in solution. Glassy carbon electrodes coated with films of mercury [100,121-124], but also of gold [101,125], are used. As reference served calomel or silver/silver chloride electrodes [121]. Platinum foils or wires were used as counterelectrodes. At -0.7 V carbon electrodes are precoated with mercury from acid Hg(II) or gold from acid Au(III) solutions. To deposit Bi on the electrode -0.2 to -0.3 V is a sufficient potential for preelectrolysis, but mostly higher voltages are chosen to determine other metals as well. Bi is stripped fiom the electrode at potentials of about -0.10 to -0.16 V. Only some elements interfere with Bi, such as arsenic, mercury, copper, and antimony. Copper interferes at high concentrations and is separated by extraction [101]. Arsenic or antimony in urine are oxidized to their pentavalent states [125]. 

American Association of Cereal Chemists adsorptive stripping voltammetry silver liquid amalgam film-modified silver solid amalgam annular band electrode... 

Cathodic stripping voltammetry (CSV) is the inverse of ASV. Mercury electrodes can be used to detect and quantify species that form sparingly soluble mercury salts such as halide ions, sulfide, cyanide, thiols, and penicillins. CSV is not restricted to mercury electrodes. Any electrode material that, on oxidizing, forms sparingly soluble salts will work, such as silver electrodes for the determination of halide ions. Another possibility is that the ion of interest oxidizes to form a precipitate on the electrode surface. 

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