Stripping voltammetry accumulation

Stripping voltammetry involves the pre-concentration of the analyte species at the electrode surface prior to the voltannnetric scan. The pre-concentration step is carried out under fixed potential control for a predetennined time, where the species of interest is accumulated at the surface of the working electrode at a rate dependent on the applied potential. The detemiination step leads to a current peak, the height and area of which is proportional to the concentration of the accumulated species and hence to the concentration in the bulk solution. The stripping step can involve a variety of potential wavefomis, from linear-potential scan to differential pulse or square-wave scan. Different types of stripping voltaimnetries exist, all of which coimnonly use mercury electrodes (dropping mercury electrodes (DMEs) or mercury film electrodes) [7, 17]. 

Analytical Applications In addition to the above-mentioned analytical aspects of the processes at Hg electrodes, in this section, we briefly review the papers focused on the subject of the affinity of various compounds to the mercury electrode surface, which allowed one to elaborate stripping techniques for the analysis of inorganic ions. Complexes of some metal ions with surface-active ligands were adsorptively accumulated at the mercury surface. After accumulation, the ions were determined, usually applying cathodic stripping voltammetry (CSV). Representative examples of such an analytical approach are summarized as follows. 

The Co(II) -phenylthiourea-borax buffer system has been studied applying CSV at HMDE [69]. An irreversible peak observed at —1.5 V was attributed to the catalytic hydrogen evolution. The first reduction step, combined with the adsorptive accumulation of herbicide metribuzin at mercury electrode, has been used for its determination by adsorptive stripping voltammetry [70]. 

Ivanov and Kaplun [76] used catechol in the determination of vanadium by adsorptive stripping voltammetry. It has been shown that the studied electrode process comprised one-electron reversible reduction of vanadium (IV) triscatecholate, previously accumulated at the electrode. It has also been found that the reduced... 

Lovric M, Komorsky-Loviic S (1989) Theory of square-wave stripping voltammetry with adsorptive accumulation. Fresenius J Anal Chem 334 289-294. 

Cathodic stripping voltammetry (CSV) involves anodic (oxidative) deposition of an insoluble film of material on the electrode it is subsequently stripped off during a negative-going potential sweep [9]. Most CSV applications rely on the anodic accumulation of sparingly soluble mercury compounds on a mercury surface ... 

The four variations of this technique are to be found in Table 14.2. The schemes of operation are shown in Fig. 14.6. Important applications for trace metals are the use of anodic stripping voltammetry (ASV) to determine trace quantities of copper, cadmium, lead and zinc, and adsorptive stripping voltammetry (AdSV) of trace quantities of nickel and cobalt—pre-concentration by adsorption accumulation of the oxime complexes followed by reduction to the metal is employed, as reoxidation of these metals in ASV is kinetically slow and does not lead to well-defined stripping peaks. 

Electroactivity (electroactive or electrochemically active compounds) — The capability of a substance to take part in a faradaic electrode reaction. Electroactive compounds can be in the gaseous, liquid, or solid state or they may be dissolved in (liquid or solid) solutions. Various compounds are also electroactive in the adsorbed state (see -> adsorption, - adsorptive accumulation, -> adsorptive stripping voltammetry) or as polymer films (see -> polymer-modified electrodes) on electrodes. 

Accumulation potential — is the value of potential for accumulating a certain reagent at the electrode surface or in the electrode volume (for instance in an - amalgam or when using the electroanalytical technique known as - stripping voltammetry. 

Potentiodynamic sensors are based on the measurement of the current response of the working electrode under no mass transport limiting conditions. Potentiodynamic methods typically involve accumulation (or preconcentration) steps, such as in stripping voltammetry for analyzing trace metals in solution. 

Signals obtained with linear-sweep voltammetry are less sensitive than those obtained with the differential-pulse technique. Therefore, the time needed for accumulating a sufficient amount of the preelectrolysis product is typically 10-60 min for the linear-sweep technique as opposed to 30 sec to 5 min for the differential-pulse mode. Since it is more difficult to control the conditions of the electrolysis over a prolonged period of time, the results obtained with differential-pulse voltammetry are usually more reproducible than those obtained with linear-sweep stripping voltammetry. 

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